Precursor dielectric composition with thiosulfate-containing polymers

ABSTRACT

A precursor dielectric composition comprises: (1) a photocurable or thermally curable thiosulfate-containing polymer that has a T g  of at least 50° C. and comprises: an organic polymer backbone comprising (a) recurring units comprising pendant thiosulfate groups; and organic charge balancing cations, (2) optionally, an electron-accepting photosensitizer component, and (3) one or more organic solvents in which the photocurable or thermally curable thiosulfate-containing polymer is dissolved or dispersed. These precursor dielectric compositions can be applied to various substrates and eventually cured to form dielectric compositions or layers for various types of electronic devices.

RELATED APPLICATIONS

Reference is made to the following copending and commonly assignedpatent applications, the disclosures of which are incorporated herein byreference:

U.S. Ser. No. 14/301,375 (filed on Jun. 11, 2014 by Shukla and Donovan),and entitled “Photocurable and Thermally Curable Thiosulfate-containingPolymers;”

U.S. Ser. No. 14/301,380 (filed on Jun. 11, 2014 by Shukla, Mis, andDonovan), and entitled “Thiosulfate-containing Polymers Associated withPhotosensitizer Component;”

U.S. Ser. No. 14/301,370 (filed Jun. 11, 2014 by Shukla, Donovan, andMis), and entitled “Devices Having Dielectric Layers with ThiosulfatePolymers.”

FIELD OF THE INVENTION

This invention relates to various precursor dielectric compositions thatcan be used to prepare various devices such as organic field effecttransistors (OFET's) containing crosslinked disulfide polymers derivedfrom unique photocurable or thermally curable thiosulfate-containingpolymers that comprise neutralizing organic cations. The crosslinkeddisulfide polymers provide dielectric materials or gate dielectric inthe devices.

BACKGROUND OF THE INVENTION

A typical field effect transistor (FET) comprises a number of layers andthey can be configured in various ways. For example, an FET may comprisea substrate, a dielectric, a semiconductor, source and drain electrodesconnected to the semiconductor and a gate electrode. When voltage isapplied between the gate and source electrodes, charge carriers areaccumulated in the semiconductor layer at its interface with thedielectric resulting in the formation of a conductive channel betweenthe source and the drain and current flows between the source and thedrain electrode upon application of potential to the drain electrode.

FET's are widely used as a switching element in electronics, forexample, in active-matrix liquid-crystal displays, smart cards, and avariety of other electronic devices and components thereof. The thinfilm transistor (TFT) is an example of a field effect transistor (FET).The best-known example of an FET is the MOSFET(Metal-Oxide-Semiconductor-FET), today's conventional switching elementfor high-speed applications. Presently, most thin film devices are madeusing amorphous silicon as the semiconductor. Amorphous silicon is aless expensive alternative to crystalline silicon. This fact isespecially important for reducing the cost of transistors in large-areaapplications. Application of amorphous silicon is limited to low speeddevices, however, since its maximum mobility (0.5-1.0 cm²/V·sec) isabout a thousand times smaller than that of crystalline silicon.

Although amorphous silicon is less expensive than highly crystallinesilicon for use in TFT's, amorphous silicon still has its drawbacks. Thedeposition of amorphous silicon, during the manufacture of transistors,requires relatively costly processes, such as plasma enhanced chemicalvapor deposition and high temperatures (about 360° C.) to achieve theelectrical characteristics sufficient for display applications. Suchhigh processing temperatures disallow the use of substrates, fordeposition, made of certain plastics that might otherwise be desirablefor use in applications such as flexible displays.

In the past two decades, organic materials have received significantattention as a potential alternative to inorganic materials, such asamorphous silicon, for use in semiconductor channels of FET's. Comparedto inorganic materials, that require a high-temperature vacuum process,organic semiconductor materials are simpler to process, especially thosethat are soluble in organic solvents and, therefore, capable of beingapplied to large areas by far less expensive processes, such asroll-to-roll coating, spin coating, dip coating and micro-contactprinting. Furthermore organic materials may be deposited at lowertemperatures, opening up a wider range of substrate materials, includingplastics, for flexible electronic devices. Accordingly, thin filmtransistors made of organic materials can be viewed as a potential keytechnology for plastic circuitry in display drivers, portable computers,pagers, memory elements in transaction cards, and identification tags,where ease of fabrication, mechanical flexibility, and/or moderateoperating temperatures are important considerations. However, to realizethese goals, OFET semiconductor and dielectric components should ideallybe easily manufactured using high-throughput, atmospheric pressure,solution-processing methods such as spin-coating, casting, or printing.

To date in the development of organic field effect transistors (OFET's)considerable efforts have been made to discover new organicsemiconductor materials and optimizing properties of such materials.These efforts have been quite fruitful and a number of organicsemiconducting materials have been designed and, to a lesser extent,structure-property relationships of such materials have been studied.

Accordingly, fused acenes such as tetracene and pentacene, oligomericmaterials containing thiophene or fluorene units, and polymericmaterials like regioregular poly(3-alkylthiophene) have been shown toperform in OFET's as “p-type” or “p-channel,” semiconductors, meaningthat negative gate voltages, relative to the source voltage, are appliedto induce positive charges (holes) in the channel region of the device.Examples of acene and heteroacenes based semiconductors are well knownin the prior art.

As an alternative to p-type organic semiconductor materials, n-typeorganic semiconductor materials can be used in FET's where theterminology “n-type” or “n-channel” indicates that positive gatevoltages, relative to the source voltage, are applied to induce negativecharges in the channel region of the device. For example, n-typesemiconductors based on diimide materials are known in the art.

The overall performance of an OFET is dependent on a number of factorssuch as the degree of crystallization and order of organic semiconductorlayer, charge characteristics, and trap density at the interfacesbetween dielectric and organic semiconductor layers, and the carrierinjection ability of the interfaces between source/drain electrodes andorganic semiconductor layers. Although, the gate dielectric layer isintended to ensure a sufficiently good electrical insulation between thesemiconductor and the gate electrode, it plays an important role in theoverall performance of an OFET. In particular, the gate dielectricpermits the creation of the gate field and the establishment of thetwo-dimensional channel charge sheet. Upon application of a source-drainbias, the accumulated charges move very close to thedielectric-semiconductor interface from the source electrode to thedrain electrode.

Since the charge flow in organic semiconductor occurs very close (˜1 nm)to the dielectric interface, it is important to optimize chemical andelectrical behavior of the dielectric layer. Besides these factors, thedielectric surface morphology has a great effect on carrier or chargemobility of the semiconductor. The surface morphology of the dielectricmaterial and variations in its surface energies [for example, surfacetreatment via self-assembled monolayers (SAMs)] have been shown tomodify the growth, morphology, and microstructure of thevapor/solution-deposited semiconductor, each of these being a factoraffecting mobility and current on/off ratio, the latter being thedrain-source current ratio between the “on” and “off” states, anotherimportant device parameter. The properties of the dielectric materialcan also affect the density of state distribution for both amorphous andsingle-crystal semiconductors.

Gate dielectric materials for OFET's can be divided into inorganic andorganic materials. Inorganic dielectric materials like silicon oxide(SiO₂), silicon nitride (SiN_(x)), aluminum oxide (AlO_(x)), andtantalum oxide (TaO_(x)) are conventionally deposited via chemical vapordeposition (CVD) and plasma enhanced CVD methods which are hightemperatures (>300° C.) processes and not compatible with polymericsubstrates. Lower processing temperatures usually lead to poor qualityfilms with pinholes, resulting in poor insulating properties. As aresult it is necessary to use thick layers (more than 100 nm) to ensuresufficiently good insulator properties which results in increased supplyvoltages for operation of such circuits. Another widely used process ision beam deposition, but it needs high vacuum and expensive equipmentthat are incompatible with the goal of very low cost production.Similarly, use of other high dielectric constant inorganic materials asbarium zirconate titanate (BZT) and barium strontium titanate (BST) needeither a high firing temperature (400° C.) for the sol-gel process, orradiofrequency magnetron sputtering, which also requires vacuumequipment, and can also have stoichiometric problems.

In addition to higher temperature processing, inorganic insulatinglayers generally require interfacial modification before they can beused with an organic semiconductor. It has been shown that the presenceof polar functionalities (like —OH groups on SiO₂ surface) at thedielectric-organic semiconductor interface trap charges which results inlowers carrier mobility in organic semiconductors. This is especiallytrue for n-type organic semiconductors and OFET devices comprisingn-type semiconductors. For example, a silicon dioxide dielectric surfaceis commonly functionalized with long alkyl chain silanes [commonlyoctadodecyl trichlorosilane (OTS)] using a solution phase self assemblyprocess. This results in a low energy dielectric surface with very fewchemical defects or reactive functionalities that could adversely affectthe OFET device performance.

Most organic materials used in OFET's cannot withstand the highprocessing temperatures used with conventional inorganic materials. Forexample, the 200° C. or higher temperatures needed to processconventional inorganic materials would at the very least cause apolymeric substrate to deform, and might cause further breakdown of thepolymer or even ignition at high enough temperatures. Deformation ishighly undesirable, since each layer of the structure has to becarefully registered with the layers below it, which becomes difficultto impossible when the layers below it are deformed due to processingtemperatures.

As an alternative to inorganic gate dielectrics, insulating polymershave been proposed for fabrication of OFET's. Polymers generally havethe advantage that they can be processed at relatively low temperaturesbelow 200° C. However, compared to inorganic dielectrics, the insulatingproperty of thin layers of polymeric dielectrics is usually poor onaccount of leakage currents. Hence, comparatively thick layers (morethan 100 nm) of polymeric dielectrics are usually employed infabrication of OFET's. As a consequence, integrated circuits havingOFET's with polymeric gate dielectrics require the use of comparativelyhigh supply voltages. In pentacene layers deposited on polymericdielectrics, the mobility of the charge carriers is similar or higher incomparison with inorganic dielectrics.

A number of polymers have been used as gate dielectrics in OFET's. Haliket al. (Journal of Applied Physics 93, 2977 (2003)) describe the use ofpoly(vinyl phenol) (PVP) that is thermally cross-linked withpolymelamine-co-formaldehyde as a gate dielectric layer to make p-typeOFET's. However, this attempt is limited in usefulness since a hightemperature of about 200° C. is required to attain crosslinking.Similarly, U.S. Patent Application Publication 2010-0084636 (Lin et al.)describes a photosensitive dielectric material comprising a poly(vinylphenol) based polymer, a crosslinking agent, and a photoacid generator.However, the presence of acid is not desirable since it could havedeleterious effect on the performance of OFET's.

U.S. Pat. No. 7,298,023 (Guillet et al.) describes the use of organicinsulator (or dielectric) comprising a base copolymer of PVDC-PAN-PMMAhaving the general formula(—CH₂Cl₂—)_(x)-(—CH₂CH(CN)—)_(y)-(CH₂C(CH₃)(CO₂CH₃)_(z), wherein x, y,z, in each case (independently from one another) can assume valuesbetween 0 and 1, for use in OFET's and organic capacitors. However, thepresence of polar groups at the dielectric interface creates dipolardisorder that lowers the carrier mobility.

U.S. Patent Application Publication 2008-0283829 (Kim et al.) disclosesan organic insulator composition comprising a crosslinking agent and ahydroxyl group-containing oligomer or hydroxyl group-containing polymer.However, the presence of hydroxyl groups at the organic semiconductorgate dielectric interface is not desirable as hydroxyl trap charges.

U.S. Pat. No. 6,232,157 (Dodabalapur et al.) discloses the use of apolyimide as material for organic insulating films. U.S. Pat. No.7,482,625 (Kim et al.) discloses a thermosetting composition for organicpolymeric gate insulating layer in OFET's. U.S. Pat. No. 7,482,625 alsodescribes blending polyvinyl phenol with another polymer inconsideration of physical, chemical, and electrical characteristics. Thepolymers that can be blended include polyacrylates, poly(vinyl alcohol),polyepoxys, polystyrene, and poly(vinyl pyrrolidone). U.S. Pat. No.7,741,635 (Kim et al.) describes photo-crosslinkable polymer dielectriccomposition comprising an insulating organic polymer such as poly(methylmethacrylate) (PMMA), poly(vinyl alcohol) (PVA), poly(vinyl pyrrolidone)(PVP), or poly(vinyl phenol) (PVPh) and a copolymer thereof, acrosslinking monomer having two or more double bonds, and aphotoinitiator. U.S. Patent Application Publication 2008-0161464 (Markset al.) discloses a crosslinked polymeric composition as gate dielectricmaterial.

EP 1,679,754A1 (Kim et al.) describes coating a surface of a crosslinkedpoly(vinyl phenol) gate dielectric with a thin film of fluorinecontaining polymer. Although OFET device performance may improve in thepresence of fluorine containing polymer, the process requiresundesirably coating multiple polymer layers. U.S. Pat. No. 7,352,038(Kelley et al.) describes an OFET comprising a substantiallynonfluorinated polymeric layer interposed between a gate dielectric andan organic semiconductor layer.

U.S. Pat. No. 7,528,448 (Bailey et al.) describes a multilayer thermalimaging dielectric donor composition of a dielectric layer comprisingone or more dielectric polymers such as acrylic and styrenic polymersand heteroatom-substituted styrenic polymers.

WO2007-129832 (Lee et al.) describes a composition for forming a gateinsulating layer of an OFET comprising an acrylate polymer and showmobilities in the range of 0.19-0.25 cm²/V·sec, which are significantlylower than those reported for poly(methyl methacrylate) dielectriccompositions.

While a number of dielectric compositions and materials have beenproposed for uses in OFET devices, polymer dielectric materials thatwork well in p-type or p-channel OFET's usually do not necessarilyperform as well with OFET's comprising n-type semiconductors. It hasbeen proposed that the presence of reactive chemical functionalities anddipoles at the semiconductor-polymer dielectric interface have much moresignificant effect on n-type semiconductors than p-type semiconductors.U.S. Pat. No. 7,638,793 (Chua et al.) describes that for an n-channel orambipolar OFET the organic gate dielectric layer forming an interfacewith the semiconductive layer; should have less than 10¹⁸ cm⁻³ bulkconcentration of trapping groups, and the use of poly(siloxanes) (forexample Cyclotene® electrical polymer), poly(alkenes), andpoly(oxyalkylenes) as dielectric materials.

Although various polymer dielectric compositions are known, a number ofproblems still remain in terms of the process of making such dielectriclayers and improving overall performance in OFET's. As discussed before,some the polymer dielectric compositions require coating of multiplelayers that is a difficult and costly process. Other examples ofdielectric compositions include thermosetting polymers comprisingpoly(vinyl phenol) as the main component and require a high temperatureannealing and crosslinking process. It is difficult to crosslink allphenolic groups during thermal annealing and thus the presence ofphenolic groups in dielectric is not desirable.

Furthermore, most polymer materials are usually not appropriate for usein low voltage applications due to their low dielectric constant (k).There have been many attempts to obtain a high capacitance with gatedielectrics by reducing their thickness or using polymer-inorganiccomposites to increase the dielectric constant (k) to produce lowvoltage operating OFET's.

For example, Japanese Patent 3,515,507 (Aoki et al.) discloses anorganic polymer and an inorganic material that are mixed to provideinsulating film with flexibility and high dielectric constant. Inaccordance with this reference, a powder obtained by mechanicallygrinding a ferroelectric material such as barium titanate is dispersedin an organic polymer to compensate the dielectric constant of theresulting insulated gate film and hence lower the gate voltage requiredfor the operation of OFET. However, when this method is used, thethickness of the insulating film is limited to the size of the inorganicmaterial thus ground. Furthermore, since a solid material is dispersedin an organic polymer solution, an uneven dispersion is formed, possiblycausing the generation of local electric field and concurrent dielectricbreakdown during the operation of transistor. Importantly, since theinorganic material is merely present in the organic polymer and thusdoes not compensate the chemical resistance of the insulating film, theresulting insulating film cannot be subjected to any processes involvingthe use of solvents.

Japanese Patent Publication 2003-338551 (Shindo) discloses a techniqueof forming a thin ceramic film as an insulating film on the surface ofsilicon wafer by a sol-gel method allowing a low temperature treatment.The resulting thin ceramic film can be prevented from being cracked,making it possible to efficiently produce electronic parts having a highreliability. However, the thin ceramic film is an insulating film madeof an inorganic material that can be applied to silicon wafer, which isnonflexible and hard, but it cannot be applied to flexible substrates.

U.S. Patent Application 2010-0230662 (Chen et al.) discloses gateinsulating layer comprising an azole-metal complex compound. However,pentacene based OFET having an azole-metal complex compound as adielectric shows lower mobility and poor current on/off ratio.

U.S. Patent Application 2010-0051917 (Kippelen et al.) disclosesembodiments of OFET's having a gate insulator layer comprising organicpolymer, specifically poly(vinyl phenol) (PVP), nanocompositesincorporating metal oxide nanoparticles (for example, barium titanate(BaTiO₃), strontium titanate (SrTiO₃), and barium zirconium titanate(BaZrTiO₃)) coated by organic ligands and methods of fabricating suchOFET's.

Usually dispersions of metal oxide nanoparticles in a polymer matrix arenot homogeneous. In an attempt to obtain a uniformly dispersedorganic-inorganic mixture system as an ordinary material technique, ithas been practiced to prepare a composite film from a mixture of asolution of metal alkoxide that is a precursor of inorganic oxide and anorganic polymer solution by a sol-gel method. In this case, it isexpected that as the dispersion of organic polymer is made more onmonomolecular level, the thermal stability of the organic polymer ismore enhanced. Thus, when a polymer or molecules capable of makinghydrogen bond such as hydroxyl group or electrostatic mutual action arepresent in a metal alkoxide solution, a sol-gel polycondensation isformed selectively on the surface of the compound to form a dried gel.

A composite film comprised of poly(methyl methacrylate-co-methacrylicacid) (PMMA-co-MAA)/sol-gel-derived TiO₂ has been used as gatedielectric layer in pentacene based OFET's. However, surface roughnessof such films is quite high (about 2.1 nm). In the case of deposition ofsmall semiconductor molecules, such as pentacene, molecular orientationand grain morphology depend strongly on the surface roughness and energyof the underlying film. Surface smoothness ofpoly(4-vinylphenol)-composite is better (about 1.3 nm) and pentaceneOFETs show smaller threshold voltage (Kim et al. J. Am. Chem. Soc. 132,14721, 2010).

Although various polymer dielectric compositions are known, a number ofproblems still remain in terms of the process of making such dielectriclayers and improving overall performance in OFET's. As discussed before,to increase the dielectric constant of polymer dielectric materials, anumber of polymer-inorganic composites, by adding metal oxidenanoparticles and making metal oxide nanoparticles by sol-gel method,are known. However, these methods do not result in crosslinking of thedielectric layer, which is a key requirement in solution processableOFET's. To achieve crosslinking photocurable resins have to be used.

Since most of the polymer dielectrics known in prior art are notcrosslinked, the resulting dielectric film cannot be subjected to anyprocesses involving the use of solvents. To address this problem variouscross linked polymer dielectrics have been developed for example asdescribed by Halik et al. [Journal of Applied Physics 93, 2977 (2003)].In addition, U.S. Pat. No. 7,482,625 (Kim et al.) describes blendingpolyvinyl phenol with another polymer for certain physical, chemical andelectrical characteristics. However, this approach has limitedapplication since a high temperature of about 200° C. is required toattain crosslinking.

Thus, there is a need for polymer dielectric materials that are solublein environmentally friendly solvents, easy to apply as a single layer,that exhibit good electrical and insulating properties, and that can beprepared from commercially available polymer or molecular precursorsusing solution processes at low temperatures and atmospheric pressures.It is also desired that they have higher dielectric constant (k) andcould be thermally and/or photochemically crosslinked. It is difficultto find polymeric materials that have all of these properties becausesome polymers will exhibit improvements in some of the properties butexhibit worse effects in others.

With the difficulty in balancing all desired properties in mind, therecontinues to be research to find useful polymeric dielectric materials.

SUMMARY OF THE INVENTION

To address the problems noted above, the present invention providesprecursor dielectric compositions, each of which comprises:

(1) a photocurable or thermally curable thiosulfate-containing polymerthat has a T_(g) of at least 50° C. and comprises: an organic polymerbackbone comprising (a) recurring units comprising pendant thiosulfategroups; and organic charge balancing cations,

(2) optionally, an electron-accepting photosensitizer component, and

(3) one or more organic solvents in which the photocurable or thermallycurable thiosulfate-containing polymer is dissolved or dispersed.

The present invention provides precursor dielectric compositionscontaining thiosulfate-containing polymers that overcome deficiencies inorganic polymers used as dielectric layers in the art. The presentinvention provides materials for improving the properties of organicfield effect transistors (OFET's) including n-type or p-type organicfield effect thin film transistors, using improved organic film-formingpolymeric precursor dielectric materials.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1a through 1d illustrate cross-sectional views of four possibleconfigurations for an organic field effect transistor according to atleast one embodiment of the present invention. FIGS. 1a and 1billustrate a device having a bottom gate configuration and FIGS. 1c and1d illustrate a device having a top gate configuration.

FIG. 2 illustrates general crosslinking or curing schemes.

DETAILED DESCRIPTION OF THE INVENTION

The following discussion is directed to various embodiments of thepresent invention and while some embodiments can be desirable forspecific uses, the disclosed embodiments should not be interpreted orotherwise considered to limit the scope of the present invention. Inaddition, one skilled in the art will understand that the followingdisclosure has broader application than is explicitly described and thediscussion of any embodiment is not intended to limit the scope of thepresent invention.

Definitions

As used herein to define various components of the precursor dielectriccompositions, gate dielectric layers, semiconductor thin films, andother formulations, unless otherwise indicated, the singular forms “a”,“an”, and “the” are intended to include one or more of the components(that is, including plurality referents).

Each term that is not explicitly defined in the present application isto be understood to have a meaning that is commonly accepted by thoseskilled in the art. If the construction of a term would render itmeaningless or essentially meaningless in its context, the termdefinition should be taken from a standard dictionary.

The use of numerical values in the various ranges specified herein,unless otherwise expressly indicated otherwise, are considered to beapproximations as though the minimum and maximum values within thestated ranges were both preceded by the word “about”. In this manner,slight variations above and below the stated ranges can be used toachieve substantially the same results as the values within the ranges.In addition, the disclosure of these ranges is intended as a continuousrange including every value between the minimum and maximum values.

As used herein, the terms “over,” “above,” and “under” and other similarterms, with respect to layers in the devices described herein, refer tothe order of the layers, wherein the organic thin film layer is abovethe gate electrode, but do not necessarily indicate that the layers areimmediately adjacent or that there are no intermediate layers.

Moreover, unless otherwise indicated, percentages refer to percents bytotal dry weight, for example, weight % based on total solids of eithera layer or formulation used to make a layer. Unless otherwise indicated,the percentages can be the same for either the dry layer or the totalsolids of the formulation used to make that layer.

For clarification of definitions for any terms relating to polymers,reference should be made to “Glossary of Basic Terms in Polymer Science”as published by the International Union of Pure and Applied Chemistry(“IUPAC”), Pure Appl. Chem. 68, 2287-2311 (1996). However, anydefinitions explicitly set forth herein should be regarded ascontrolling.

Unless otherwise indicated, the term “polymer” refers to high and lowmolecular weight polymers including oligomers and includes homopolymersand copolymers.

The term “copolymer” refers to polymers that comprise two or moredifferent recurring units, and for vinyl polymers can be derived fromtwo or more ethylenically unsaturated polymerizable monomers.

Unless otherwise indicated, the term “mol %” when used in reference torecurring units in polymers, refers to either the nominal (theoretical)amount of a recurring unit based on the molecular weight ofethylenically unsaturated polymerizable monomer used in thepolymerization process, or to the actual amount of recurring unit in theresulting polymer as determined using suitable analytical techniques andequipment.

The term “organic backbone” refers to the chain of atoms (carbon orheteroatoms) in a polymer to which a plurality of pendant groups,including thiosulfate groups, can be attached. One example of such abackbone is an “all carbon” backbone obtained from the polymerization ofone or more ethylenically unsaturated polymerizable monomers. However,other backbones can include heteroatoms wherein the polymer is formed bya condensation reaction or by some other means.

The term “recurring unit” refers to a distinct unit or segment in apolymer, which can be the same or different as other distinct units, andwhich recurring units can be derived or created in the polymer usingknown techniques. Recurring units are generally present in multipleplaces along the organic polymer backbone and can occur randomly or inblocks.

A “thiosulfate” group is a substituent defined by the followingStructure (TS):

Any polymer comprising this thiosulfate group in pendant groups iscalled a “thiosulfate polymer” or “thiosulfate-containing polymer” inthe description of the present invention. When the thiosulfate group isassociated with a charge balancing cation (M⁺), the resulting materialis considered a Bunte salt.

The term “photocurable or thermally curable thiosulfate-containingpolymer” refers to the polymers described below that are useful in thepractice of this invention and comprise one or more pendant thiosulfategroups connected to a suitable polymer backbone.

Unless otherwise indicated, the term “crosslinked disulfide polymer”refers to the materials that result from photocuring or thermally curingthe photocurable or thermally curable thiosulfate-containing polymersdescribed below. In general, such crosslinked disulfide polymers or the“photochemically or thermally crosslinked product” described hereincomprises less than 10 mol % of the original pendant thiosulfate groupsthat are not crosslinked, or more typically less than 2 mol % of suchoriginal pendant thiosulfate groups that are not crosslinked.

Unless otherwise indicated, the terms “dielectric layer” and “gatedielectric layer” are intended to mean the same thing.

The above described features and advantages of the present inventionwill become more apparent when taken in conjunction with the followingdescription and drawings wherein identical reference numerals have beenused, where possible, to designate identical or analogous features thatare common to the Figures.

Photocurable or Thermally Curable Thiosulfate-Containing Polymers

The photocurable or thermally curable thiosulfate polymers useful inthis invention comprise (a) recurring units comprising pendantthiosulfate groups suitable to provide sufficient disulfide bonds uponcrosslinking. These photocurable or thermally curablethiosulfate-containing polymers can be formed from a precursor polymerthat has precursor pendant thiosulfate groups (described below) that canbe suitably reacted to provide the essential pendant thiosulfate groupsattached to polymer backbone. In some embodiments, the photocurable orthermally curable thiosulfate-containing polymer comprises (a) recurringunits in an amount of at least 0.5 mol % and up to and including 50 mol%, based on the total recurring units in the photocurable or thermallycurable thiosulfate-containing polymer. Other useful embodiments aredescribed in more detail below.

In all embodiments of the photocurable or thermally curablethiosulfate-containing polymers useful in the present inventiongenerally have multiple (two or more) pendant thiosulfate groups(—S—SO₃M groups) distributed randomly or in blocks of recurring unitsalong the chain of atoms forming the organic polymer backbone.

In some embodiments, the photocurable or thermally curablethiosulfate-containing polymers have charge balancing cations that formbinary salts with the pending thiosulfate groups in the (a) recurringunits. For example, such embodiments can be represented by recurringunits represented by the following Structure (I):

wherein R represents a suitable organic polymer backbone. Usefulpolymers that comprise the R organic polymer backbone are described inmore detail below. For example, the useful polymers can be formed asvinyl polymers having entirely carbon atoms in the organic polymerbackbone, and which contain one or more different recurring unitsderived from one or more ethylenically unsaturated polymerizablemonomers using emulsion or suspension polymerization techniques.Alternatively, the R organic polymer backbone can have carbon, oxygen,sulfur, or nitrogen atoms and be formed from condensation reactionsusing appropriate reactive compounds (for example diols with diacids toform polyester or diamines with diols to form polyamides). For example,the R organic polymer backbone can be a polyurethane backbone.

In Structure (I), G is a single bond or a suitable divalent linkinggroup that is attached to a polymer backbone. Useful G divalent linkinggroups include but are not limited to, —(COO)_(p)—(Z)_(q)— wherein p andq are independently 0 or 1. Z can be a substituted or unsubstituteddivalent aliphatic group having 1 to 6 carbon atoms including alkylenegroups (such as methylene, ethylene, n-propylene, isopropylene,butylenes, 2-hydroxypropylene and 2-hydroxy-4-azahexylene), whichdivalent aliphatic group can comprise one or more oxygen, nitrogen orsulfur atoms in the chain (such as carbonamido, sulfonamido,alkylenecarbonyloxy, ureylene, carbonyloxy, sulfonyloxy, oxy, dioxy,thio, dithio, seleno, sulfonyl, sulfonyl, and imido), a substituted orunsubstituted arylene group having 6 to 14 carbon atoms in the aromaticring (such as phenylene, naphthalene, anthracylene, and xylylene), asubstituted or unsubstituted combination of alkylene and arylene groupssuch as substituted or unsubstituted arylenealkylene or alkylenearylenegroups having at least 7 and to and including 20 carbon atoms in thechain (such as p-methylenephenylene, phenylenemethylenephenylene,biphenylene, and phenyleneisopropylene-phenylene), or a heterocyclicring (such as pyridinylene, quinolinylene, thiazolinylene, andbenzothioazolylene). In addition, G can be a substituted orunsubstituted alkylene group, a substituted or unsubstituted arylenegroup, in a substituted or unsubstituted arylenealkylene group oralkylenearylene group, having the same definitions as Z.

In Structure (I), “a” represents at least 0.5 mol % and up to andincluding 100 mol % of (a) recurring units, based on the total recurringunits in the photocurable or thermally curable thiosulfate-containingpolymer. In many embodiments, “a” represents at least 0.5 mol % and upto and including 90 mol %, or at least 5 mol % and up to and including75 mol %, or even up to and including 50 mol % of (a) recurring units,all based on the total recurring units in the photocurable or thermallycurable thiosulfate-containing polymer.

M (can also be represented herein as M⁺) represents a suitable chargebalancing cation such as a metal cation or an organic cation includingbut not limited to, an alkali metal ion (lithium, sodium, potassium, andcesium), quaternary ammonium, pyridinium, morpholinium, benzolium,imidazolium, alkoxypyridinium, thiazolium, and quinolinium monovalentcations. Divalent cations can be present in small amounts so thatpremature crosslinking of the thiosulfate polymer is minimized but inmost embodiments, M is a monovalent charge balancing cation such as apotassium ion, sodium ion, pyridinium ion or thiazolium ion. In otherembodiments, the organic charge balancing cations are particularlyuseful, including but not limited to, ammonium, pyridinium,morpholinium, benzolium, imidazoliuni, alkoxypyridinium, thiazolium, andquinolinium monovalent cations.

Any photocurable or thermally curable thiosulfate-containing polymercontaining one or more thiosulfate groups as described herein can beused in the present invention. For example, suitable photocurable orthermally curable thiosulfate-containing polymers can include but arenot limited to, vinyl polymers derived at least in part frommethacrylate or acrylate ethylenically unsaturated polymerizablemonomers (known herein as “polymethacrylates” and “polyacrylates”,including both homopolymers and copolymers), polyethers, poly(vinylester)s, and polystyrenes (including homopolymers and copolymers derivedfrom styrene and styrene derivatives having one or more substituents onthe pendant benzene ring or attached along the polymer backbone). Suchphotocurable or thermally curable thiosulfate-containing polymers havean entirely carbon backbone. However, pendant thiosulfate groups can bepresent in condensation polymers including but not limited to,polyesters, polyamides, polyurethanes, polycarbonates, polymers derivedfrom cellulose esters, and polysiloxanes using chemistry that would bereadily known to one skilled in the art. In addition, thepolyamide-epichlorohydrin-Bunte salts, polyoxyalkylene-Bunte salts, andpolysiloxane-Bunte salts described in U.S. Pat. No. 5,424,062 (Schwan etal.) also can be used in the present invention.

The photocurable or thermally curable thiosulfate-containing polymerscan also include other pendant groups and various recurring units toprovide useful properties as described below for various embodiments.

In most embodiments of this invention, photocuring or thermal curing ofthe photocurable or thermally curable thiosulfate-containing polymersdescribed herein is used to produce a crosslinked disulfide polymerwherein at least 5 mol %, or at least 50 mol %, and up to and including100 mol % of the available thiosulfate groups are reacted to formdisulfide bonds between adjacent or nearby thiosulfate groups. Theproduct crosslinked disulfide polymers, however, can be obtained usingother means that would be readily apparent to one skilled in the art.

For example, photocuring can take place upon exposure of a photocurablethiosulfate-containing polymer (in a precursor dielectric composition)using suitable radiation having a λ_(max) of at least 150 nm and up toand including 1500 nm, or more likely using radiation having a λ_(max)of at least 150 nm and up to and including 450 nm, wherein the pendantthiosulfate groups are electronically excited such that they react toform disulfide bonds and crosslink within the reacted polymer.Photoexposure can be carried out using suitable sources of suchradiation for a suitable time to provide the needed curing energy. Askilled worker would know how to optimize the conditions for achievingdesired crosslinking (disulfide bond formation), for example so thatless than 10 mol % and more desirably less than 5 mol % of the originalthiosulfate groups are unreacted after the photocuring process.

Useful thermal curing processes can also be carried out by heating aprecursor dielectric composition to a temperature of at least 110° C.and up to and including 150° C. using a suitable source of heat such ahotplate, oven, infrared heating (for example, exposure to anear-infrared- or infrared-emitting laser), or other heating apparatus,for a sufficient time to obtain desired crosslinking (disulfide bondformation) such as at least 10 minutes and up to and including 30minutes. A skilled artisan can readily determine the optimal heatingtemperature and time conditions that would be desirable to achieve thedesired crosslinking.

The photocurable or thermally curable thiosulfate-containing polymer cancomprise the (a) recurring units in an amount of at least 5 mol % and upto and including 50 mol %, based on total recurring units in thephotocurable or thermally curable thiosulfate-containing polymer.

It is essential that the photocurable or thermally curablethiosulfate-containing polymers also contain suitable charge balancingcations (for example the “M” groups described above) so that the notedpolymer has an essentially net neutral charge throughout the molecule.The term “essentially net neutral charge” means that at least 95 mol %of the available thiosulfate groups are associated with (or ionicallybound to) charge balancing cations, and in most embodiments, at least 98mol % and up to and including 100 mol % of the available thiosulfategroups are thusly counterbalanced in charge.

As noted below, these charge balancing cations can be located orprovided in any suitable form or location as would be readily understoodfrom the teaching provided below. In many embodiments, they are closeenough to the pendant thiosulfate groups for charge association (orcharge balancing) to form either binary salts or zwitterionic groupswith the thiosulfate groups.

In some embodiments, the charge balancing cations are part of theorganic polymer backbone of the photocurable or thermally curablethiosulfate-containing polymer and are not part of pendant groupsattached to the organic polymer backbone.

Depending upon their location within the photocurable or thermallycurable thiosulfate-containing polymers, the charge balancing cationscan form binary salts with the pendant thiosulfate groups in the (a)recurring units and in such embodiments, the charge balancing cationscan be any suitable monovalent cations such as inorganic metal cationsincluding but not limited to, alkali metal ions such as lithium, sodium,potassium, and cesium, as well as organic monovalent cations asdescribed below. The same or different charge balancing cations can bepresent in different (a) recurring units along the organic polymerbackbone.

In some embodiments, the charge balancing cations can form zwitterionicgroups with the pendant thiosulfate groups in (a) recurring units asrepresented by the following Structure (II):

wherein R, G, and “a” are as defined for Structure (I) above. Q⁺ can bean organic charge balancing cation including but not limited to,quaternary ammonium cation, pyridinium cation, morpholinium cation,benzolium cation, imidazolium cation, alkoxypyridinium cation,thiazolium cation, and quinolinium cation. The quaternary ammoniumcations, pyridinium cations, morpholinium cations, and thiazoliumcations are particularly useful. Within such photocurable orthermally-curable thiosulfate-containing polymers, the (a) recurringunits containing the thiosulfate groups can have the same or differentorganic charge balancing cation. In other words, Q⁺ can be the same ordifferent in the various (a) recurring units along the polymer backbone.In most of such embodiments, the same organic charge balancing cation isused in all of the recurring units in a specific photocurable orthermally-curable thiosulfate-containing polymer.

Some particularly useful ethylenically unsaturated polymerizablemonomers from which (a) recurring units can be derived, include:

-   p-vinylbenzyl thiosulfate sodium salt,-   2-sodium thiosulfate ethyl methacrylate, and-   2-sodium thiosulfate propyl methacrylate.

In addition, various precursor ethylenically unsaturated polymerizablemonomers can be used to prepare precursor polymers having pendantreactive groups that can be converted to pendant thiosulfate groups.Representative monomers of this type include the following compounds:

In some embodiments, the photocurable or thermally curablethiosulfate-containing polymer comprises: (a) recurring units comprisingpendant thiosulfate groups, and (b) recurring units comprising chargebalancing cations that are associated with the (a) recurring unitssufficiently to provide a net neutral charge with the pendantthiosulfate groups, Thus, the (b) recurring units are generally presentin an amount at least equal to the (a) recurring units, but the (b)recurring units can be present in greater amounts if desired. Suchembodiments with (a) recurring units and (b) recurring units can berepresented by the following Structure (III) showing adjacent (a)recurring units and (b) recurring units:

wherein R, G, and M⁺ (also represented as M) are as defined above.Within Structure (III), “a” represents at least 0.5 mol % and up to andincluding 50 mol %, or at least 1 mol % and up to and including 40 mol%, of (a) recurring units, and “b” represents the (b) recurring unitsand is at least equal to the “a” mol % but can be greater than the “a”mol %, all based on the total recurring units in the photocurable orthermally-curable thiosulfate-containing polymers. In most of theseembodiments, the amount of (b) recurring units is essentially equal tothe amount of (a) recurring units. The term “essentially” refers to thedefinition of “essential net neutral charge” defined above.

In some embodiments, the photocurable or thermally curablethiosulfate-containing polymer that comprises the (a) recurring units inan amount of at least 0.5 mol % and up to and including 50 mol %, andthe (b) recurring units in an amount of at least 0.5 mol % and up to andincluding 50 mol % recurring units, all based on total recurring unitsin the photocurable or thermally curable thiosulfate-containing polymer.

Such (b) recurring units can be located at any point along the polymerbackbone as long as the (b) recurring units are associated with (nearto) the (a) recurring units containing the pendant thiosulfate groups.Thus, the (b) recurring units can be randomly distributed along thepolymer backbone or they can be in blocks along the polymer backbone, aslong as the M⁺ charge balancing cations (typically, organic chargebalancing cations) are able to counterbalance the associated thiosulfatenegative charges.

Useful (b) recurring units can be derived from ethylenically unsaturatedpolymerizable monomers containing suitable charge balancing cationsincluding but not limited to, quaternary ammonium cations, pyridiniumcations, morpholinium cations, and thiazolium cations.

It is also possible that useful photocurable or thermally curablethiosulfate-containing polymers can comprise (a) recurring unitsrepresented by either of both of Structures (I) and (II), along with (b)recurring units represented by Structure (III).

Still other useful photocurable or thermally curablethiosulfate-containing polymers can comprise at least (a) recurringunits, as well as (c) recurring units comprising a photosensitizercomponent R₂ as represented by Structure IV below.

wherein R′ is an organic polymer backbone, G′ is a single bond or asuitable divalent linking group that can be any of those defined for Gas noted above, R₂ is a electron-accepting photosensitizer component asdefined below, and c is at least 1 mol % and up to and including 10 mol%, or typically at least 2 mol % and up to and including 8 mol %, of (c)recurring units, all based on the total recurring units in thephotocurable or thermally curable thiosulfate-containing polymer.

For example, representative electron-accepting photosensitizercomponents can be derived from compounds that include but are notlimited to, cyano-substituted carbocyclic aromatic compounds orcyanoaromatic compounds (such as 1-cyanonaphthalene,1,4-dicyanonaphthalene, 9,10-dicyanoanthracene,2-t-butyl-9,10-dicyanoanthracene, 2,6-di-t-butyl-9,10-dicyanoanthracene,2,9,10-tricyanoanthracene, 2,6,9,10-tetracyanoanthracene), aromaticanhydrides and aromatic imides (such as 1,8-naphthylene dicarboxylic,1,4,6,8-naphthalene tetracarboxylic, 3,4-perylene dicarboxylic, and3,4,9,10-perylene tetracarboxylic anhydride or imide), condensedpyridinium salts (such as quinolinium, isoquinolinium, phenanthridinium,acridinium salts), and pyrylium salts. Useful electron-acceptingphotosensitizer components that involve the triplet excited stateinclude but are not limited to, components derived from carbonylcompounds such as quinones (for example, benzo-, naphtho-, andanthro-quinones with electron withdrawing substituents such as chloroand cyano). Ketocoumarins, especially those with strong electronwithdrawing moieties such as pyridinium, can also be used to provideelectron-accepting photosensitizer components. These compounds canoptionally contain substituents such as methyl, ethyl, tertiary butyl,phenyl, methoxy, and chloro groups that can be included to modifyproperties such as solubility, absorption spectrum, and reductionpotential.

It is also possible that the photocurable or thermally curablethiosulfate-containing polymers comprising only (a) recurring unitsrepresented by either or both of Structure (I) or (II) and (c) recurringunits represented by Structure (IV). Alternatively, the photocurable orthermally curable thiosulfate-containing polymers can comprise (a)recurring units represented by either or both of Structure (I) or (II)along with (b) recurring units represented by Structure (III) and (c)recurring units represented by Structure (IV).

Moreover, as described in more detail below, the charge balancingcations provided within the (c) recurring units represented by Structure(IV) can be the same or different from charge balancing cations that canbe present in the (a) recurring units as represented by either or bothof Structures (I) and (II), and they can be the same or different fromthe charge balancing cations present in the (b) recurring unitsrepresented by Structure (III). The noted (c) recurring unitsrepresented by Structure (IV) can thus comprise a photosensitizercomponent (as described above).

In still other embodiments, the photocurable or thermally curablethiosulfate-containing polymer can comprise (a) recurring units asdescribed above (for example, either or both Structures (I) and (II)),optionally (b) recurring units as described above (for example, asrepresented by Structure (III)), optionally (c) recurring units (forexample, as represented by Structure (IV)), but also (d) recurring unitsderived from one or more linear, branched, or carbocyclic non-aromatichydrocarbon (meth)acrylates comprising a linear, branched, orcarbocyclic non-aromatic hydrocarbon ester group comprising at least 1carbon atom and up to and including 18 carbon atoms or more likely atleast 6 carbon atoms and up to and including 18 carbon atoms.Alternatively, the (d) recurring units can also be derived from one ormore alkyl-substituted aryl (meth) acrylates in which the aryl group(such as phenyl) is substituted with one or more linear, branched orcarbocyclic non-aromatic hydrocarbon substituent(s) at least one ofwhich substituents comprises at least 6 carbon atoms and up to andincluding 18 carbon atoms. The aryl groups (such as phenyl group) aretypically not further substituted.

Such (d) recurring units can be represented by the following Structure(V):

wherein R″ represents an organic polymer backbone, G″ is a carbonyloxygroup to provide an acrylate group with R₃. R₃ comprises a monovalentlinear, branched, or carbocyclic non-aromatic hydrocarbon group having 1to 18 carbon atoms, or it comprises an aryl group (such as a phenylgroup) having one or more linear, branched, or carbocyclic non-aromatichydrocarbon substituents. At least one of these linear, branched, orcarbocyclic non-aromatic hydrocarbon substituents has at least 6 carbonatoms and up to and including 18 carbon atoms. Such aryl groups are nottypically further substituted beyond one linear, branched, orcarbocyclic non-aromatic hydrocarbon substituent.

For example, such (d) recurring units represented by Structure (V) canbe derived for example from one or more alkyl acrylates, one or morealkyl methacrylates, one or more alkyl acrylates and one or more alkylmethacrylates, or one or more arylacrylates or aryl methacrylates, whichcomprise the alkyl ester groups as defined above including but notlimited to, acrylates and methacrylates comprising n-hexyl, n-heptyl,n-octyl, n-nonyl, n-decyl, or n-dodecyl groups, branched isomersthereof, or phenyl groups substituted with at least one of such linearor branched alkyl groups.

In Structure (V), “d” represents at least 1 mol % and up to andincluding 40 mol %, or typically at least 1 mol % and up to andincluding 30 mol % of (d) recurring units, all based on the totalrecurring units in the photocurable or thermally curablethiosulfate-containing polymer.

As described above, the thiosulfate groups in the (a) recurring unitsare generally located pendant to the polymer backbone, and such groupscan be incorporated into the recurring units by appropriate reaction(described below) with precursor recurring units. The photocurable orthermally curable thiosulfate-containing polymers can comprise differentrecurring units derived from two or more different ethylenicallyunsaturated polymerizable monomers as described above for the (a), (b),(c), and (d) recurring units.

In addition to the (a), (b), (c), and (d) recurring units describedabove, the photocurable or thermally curable thiosulfate-containingpolymers can also comprise (e) recurring units that are different fromall of the noted (a) through (d) recurring units and can provide desiredfilm-forming or other properties that are not specific the dielectricfunction of the resulting crosslinked polymer. A skilled polymer chemistwould understand how to choose such optional recurring units, and forexample, they can be derived from one or more ethylenically unsaturatedpolymerizable monomers selected from the group consisting of alkylacrylates including hydroxyalkyl acrylates, alkyl methacrylatesincluding hydroxyalkyl methacrylates, (meth)acrylamides, styrene andstyrene derivatives, vinyl ethers, vinyl benzoates, vinylidene halides,vinyl halides, vinyl imides, and other materials that a skilled workerin the art would understand could provide desirable properties to thereactive polymer. Some (e) recurring units can comprise an epoxy (suchas a glycidyl group) or epithiopropyl group derived for example fromglycidyl methacrylate or glycidyl acrylate to provide additionalcrosslinking capability. If present, these (e) recurring units can bepresent in an amount of up to and including 50 mol % based on the totalrecurring units in the photocurable or thermally curablethiosulfate-containing polymer.

In some embodiments, the photocurable or thermally curablethiosulfate-containing polymer comprises at least some (a) recurringunits, and optionally (b) recurring units, but further comprises:

(c) recurring units that are represented by Structure (IV) noted above;

(d) recurring units that are represented by Structure (V) noted above;or

both (c) recurring units and (d) recurring units.

In very useful embodiments, the precursor dielectric composition ormethod used to prepare a device is designed so that:

(A) the photocurable or thermally curable thiosulfate-containing polymercomprises:

(a) recurring units that are represented by the following Structure (I)or Structure (II), or both Structures (I) and (II):

wherein R represents an organic polymer backbone, G is a single bond ordivalent linking group, Q⁺ is an organic charge balancing cation, Mrepresents a charge balancing cation, and “a” represents at least 0.5mol % and up to and including 100 mol % of (a) recurring units, based onthe total recurring units in the photocurable or thermally curablethiosulfate-containing polymer; or

(B) the photocurable or thermally curable thiosulfate-containing polymeris represented by the following Structure (III):

wherein R represents an organic polymer backbone, G is a single bond ora divalent linking group, M⁺ is a charge balancing cation, and “a” and“b” are as described above for Structure (III); and

(C) the photocurable or thermally curable thiosulfate-containing polymerof (A) or (B) optionally further comprises:

(c) recurring units that are represented by the Structure (IV) describedabove;

(d) recurring units that are represented by Structure (V) describedabove; or

both (c) recurring units and (d) recurring units.

Some particular useful photocurable or thermally curablethiosulfate-containing polymers have a glass transition temperature(T_(g)) of at least 50° C. and each comprises an organic polymerbackbone comprising:

(a) recurring units comprising pendant thiosulfate groups, based on thetotal recurring units in the photocurable or thermally curablethiosulfate-containing polymer, and

(b) recurring units comprising organic charge balancing cations that areassociated with the (a) recurring units sufficiently to provide a netneutral charge with the pendant thiosulfate groups,

which photocurable or thermally curable thiosulfate-containing polymeris represented by the following Structure (III):

wherein R represents an organic polymer backbone, G is a single bond ora divalent linking group (as described above), M⁺ represents the organiccharge balancing cation (as described above), and “a” and “b” are asdescribed above for Structure (III).

For example, the organic charge balancing cations can be selected fromquaternary ammonium, pyridinium, morpholinium, benzolium, imidazolium,alkoxypyridinium, thiazolium, and quinolinium monovalent cations.

Such photocurable or thermally curable thiosulfate polymers can befurther modified and defined wherein the (a) recurring units arerepresented by the following Structure (II):

wherein R represents an organic polymer backbone, G is a single bond ordivalent linking group (as described above), Q⁺ is an organic chargebalancing cation (as described above), and “a” is the mol % of (a)recurring units as described above.

Such photocurable or thermally curable thiosulfate polymer can furthercomprise (c) recurring units that are represented by the followingStructure (IV):

wherein R′ represents an organic polymer backbone, G′ is a divalentlinking group (as described above), R₂ is a electron-acceptingphotosensitizer component (as described above), and “c” represents atleast 1 mol % and up to and including 10 mol % of (c) recurring units,based on the total recurring units in the photocurable orthermally-curable thiosulfate-containing polymer.

In still other embodiments, such photocurable or thermally curablethiosulfate-containing polymers having (a) recurring units and either orboth (b) and (c) recurring units can further comprise (d) recurringunits that are represented by the following Structure (V):

wherein R″ represents an organic polymer backbone, G″ is a carbonyloxygroup, R₃ (as described above) comprises a monovalent linear, branched,or carbocyclic non-aromatic hydrocarbon group having 1 to 18 carbonatoms, or it comprises a phenyl group having one or more linear,branched, or carbocyclic non-aromatic hydrocarbon substituents, at leastone linear, branched, or carbocyclic non-aromatic hydrocarbonsubstituents has at least 6 carbon atoms and up to and including 18carbon atoms, and “d” represents at least 1 mol % and up to andincluding 40 mol % of (d) recurring units, based on the total recurringunits in the photocurable or thermally-curable thiosulfate-containingpolymer.

Any of these useful photocurable or thermally curablethiosulfate-containing polymers can further comprise (e) recurring unitsthat are different from (a) recurring units, (b) recurring units, (c)recurring units, and (d) recurring units, which (e) recurring units arepresent in an amount of up to and including 50 mol %, based on the totalrecurring units in the photocurable or thermally curablethiosulfate-containing polymer.

Still other useful photocurable or thermally curablethiosulfate-containing polymers have a T_(g) of at least 50° C. and eachcomprises an organic polymer backbone comprising: (a) recurring unitscomprising pendant thiosulfate groups, based on the total recurringunits in the photocurable or thermally curable thiosulfate-containingpolymer, and (d) recurring units,

which (a) recurring units are represented by either Structure (I) or(II) below, and the (d) recurring units are represented by Structure (V)below:

wherein R represents an organic polymer backbone, G is a single bond ordivalent linking group (as described above), Q⁺ is an organic chargebalancing cation (as described above), M represents a charge balancingcation (as described above), and “a” represents at least 0.5 mol % andup to and including 99.5 mol % of (a) recurring units, based on thetotal recurring units in the photocurable or thermally curablethiosulfate-containing polymer;

wherein R″ represents an organic polymer backbone, G″ is a carbonyloxygroup, R₃ (as described above) comprises a monovalent linear, branched,or carbocyclic non-aromatic hydrocarbon group having 1 to 18 carbonatoms, or it comprises a phenyl group having one or more branched, orcarbocyclic non-aromatic hydrocarbon substituents, at least one of whichhas at least 6 carbon atoms and up to and including 18 carbon atoms, and“d” represents at least 0.5 mol % and up to and including 99.5 mol % of(d) recurring units, based on the total recurring units in thephotocurable or thermally-curable thiosulfate-containing polymer.

For example, the organic charge balancing cations are selected fromquaternary ammonium, pyridinium, morpholinium, benzolium, imidazolium,alkoxypyridinium, thiazolium, and quinolinium monovalent cations.

Such useful photocurable or thermally curable thio sulfate polymers canfurther comprising (c) recurring units that are represented by thefollowing Structure (IV):

wherein R′ represents an organic polymer backbone, G′ is a single bondor a divalent linking group, R₂ is a electron-accepting photosensitizescomponent, and “c” represents at least 1 mol % and up to and including10 mol % of (c) recurring units, based on the total recurring units inthe photocurable or thermally-curable thiosulfate-containing polymer.

For example, such photocurable or thermally curablethiosulfate-containing polymers can comprises the (a) recurring units inan amount of at least 5 mol % and up to and including 30 mol % of (a)recurring units, and the (d) recurring units in an amount of at least 1mol % and up to and including 30 mol % of (d) recurring units, all basedon total recurring units in the photocurable or thermally curablethiosulfate-containing polymer.

Some of the precursor ethylenically unsaturated polymerizable monomersuseful for making these photocurable or thermally curablethiosulfate-containing polymers useful in the present invention can beobtained from various commercial sources. In other embodiments, thephotocurable or thermally curable thiosulfate-containing polymer can beprepared in several ways using understanding and reactants available toa skilled polymer chemist. For example, the useful precursor monomersand reactive ethylenically unsaturated polymerizable co-monomers can beobtained from a number of commercial sources or readily prepared, andthen polymerized using known conditions.

Thiosulfate-containing recurring units can be prepared from the reactionbetween an alkyl halide and thiosulfate salt as described in the seminalteaching of Bunte, Chem. Ber. 7, 646, 1884. Thiosulfate polymers can beprepared from preformed polymers having requisite reactive groups. Forexample, if the functional ethylenically unsaturated polymerizablemonomer is a vinyl halide polymer, the functional vinyl polymerizablemonomer can be prepared as illustrated as follows:

wherein R₁ is hydrogen or a substituted or unsubstituted alkyl groupcomprising 1 to 10 carbon atoms or an aryl group, Hal represents ahalide, and X represents a divalent linking group as defined above. Theconditions for these reactions are known in the art.

Reactive polymers containing pendant thiosulfate groups can also beprepared from preformed polymers in a similar manner as described inU.S. Pat. No. 3,706,706 (Vandenberg), the disclosure of which isincorporated herein by reference for the polymer synthetic methods:

wherein A represents the polymer backbone, Hal represents a halide, andX represents a divalent linking group as described above.

In addition, photocurable or thermally curable thiosulfate-containingpolymers containing pendant thiosulfate groups can be prepared using thereaction of an alkyl epoxide (on a preformed polymer or a functionalmonomer) with a thiosulfate salt, or between an alkyl epoxide (on apreformed polymer of a functional monomer) and a molecular containing athiosulfate moiety (such as 2-aminoethanethiosulfuric acid), asillustrated by Thames, Surf. Coating, 3 (Waterborne Coat.), Chapter 3,pp. 125-153, Wilson et al (Eds.) and as follows:

wherein R represents a substituted or unsubstituted alkyl or arylgroups. The conditions for these reactions are known in the art andrequire only routine experimentation to complete.

The mol % amounts of the various recurring units defined herein for thephotocurable or thermally curable thiosulfate-containing polymersdescribed herein are meant to refer to the actual molar amounts presentin the formed polymers. It is understood by one skilled in the art thatthe actual mol % values may differ from those theoretically possible(nominal mol %) from the amounts of ethylenically unsaturatedpolymerizable monomers that can be used in the polymerization procedure,or the reactive components used to prepare condensation polymer.However, under most polymerization conditions that allow high polymeryield and optimal reaction of all monomers, the actual mol % of eachmonomer is generally within ±15 mol % of the theoretical (nominal)amounts.

Some representative photocurable or thermally curablethiosulfate-containing polymer embodiments include but are not limitedto, the following materials wherein the molar ratios are theoretical(nominal) amounts based on the actual molar ratio of ethylenicallyunsaturated polymerizable monomers used in the polymerization process.The actual molar amounts of recurring units can differ from thetheoretical (nominal) amounts of monomers if the polymerizationreactions are not carried out to completion.

-   Poly(methacrylic acid-co-p-vinylbenzyl thiosulfate sodium salt)    (98:2);-   Poly(acrylic acid-co-p-vinylbenzyl thiosulfate sodium salt) (80:20);

Useful photocurable or thermally curable thiosulfate-containing polymersused in this invention generally have a molecular weight (M_(n)) of atleast 1,000 and up to and including 1,000,000, or typically at least10,000 and up to and including 100,000, as determined using sizeexclusion chromatography (SEC).

Useful photocurable or thermally curable thiosulfate-containing polymersused in this invention can also have a glass transition temperature(T_(g)) of at least 50° C. and up to and including 250° C. or at least70° C. and up to and including 150° C., as determined using DifferentialScanning calorimetry (DSC).

Using the teaching described above, the precursor polymers can beprepared using known free radical solution polymerization techniquesusing known starting materials, free radical initiators, and reactionconditions in suitable organic solvents that can be adapted from knownpolymer chemistry, or using known condensation polymerization processes.Where starting materials (monomers) are not available commercially, suchstarting materials can be synthesized using known chemical startingmaterials and procedures. The precursor polymers can then be reacted toform the desired thiosulfate groups to form desired photocurable orthermally curable thiosulfate-containing polymers.

Representative preparations of useful photocurable or thermally curablethiosulfate-containing polymers are provided below for the InventionExamples.

Precursor Dielectric Compositions

The photocurable or thermally curable thiosulfate-containing polymersdescribed above can be incorporated and used in precursor dielectriccompositions that are used to form precursor dielectric layers (orprecursor gate dielectric layers) as described below. Such precursordielectric layers are generally crosslinked by thermal curing orphotocuring the photocurable or thermally-curable thiosulfate-containingpolymer provided in the noted precursor dielectric composition. FIG. 2shows general photocuring and thermal curing schemes.

Each precursor dielectric composition has only one essential component,that is, one or more photocurable or thermally curablethiosulfate-containing polymers as described above that can be thermallycrosslinked (thermally cured) by heating the precursor dielectriccomposition as described above, or it can be photocrosslinked(photocured) upon exposure to radiation having λ_(max) of at least 150nm and up to and including 700 nm, or of at least 150 nm and up to andincluding 450 nm, as described above.

One or more photocurable or thermally curable thiosulfate-containingpolymers are generally present in the precursor dielectric compositionin an amount of at least 50 weight % and up to and including 100 weight%, or typically at least 90 weight % and up to and including 100 weight%, based on the total solids in the precursor dielectric composition (ortotal dry weight of the applied precursor gate dielectric layer).

The precursor dielectric compositions generally do not include separatecrosslinking agents or crosslinking agent precursors because thephotocurable or thermally curable thiosulfate-containing polymer itselfgenerally includes pendant thiosulfate groups for crosslinking (to formdisulfide bonds). However, if desired, additional crosslinking can beprovided by including recurring units in polymer backbone comprisingcrosslinkable groups such as pendant epoxy groups.

In some embodiments, the precursor dielectric composition (and resultinggate dielectric layers) can further comprise one or more photosensitizercomponents to enhance the sensitivity of photocurable or thermallycurable thiosulfate-containing polymers to specific longer wavelengths(for example, at least 300 nm and up to and including 700 nm). A varietyof photosensitizers are known in the art that can be incorporated asindividual photosensitizer components in the precursor dielectriccomposition, including but not limited to, benzothiazole andnaphthothiazole compounds as described in U.S. Pat. No. 2,732,301(Robertson et al.), aromatic ketones as described in U.S. Pat. No.4,507,497 (Reilly, Jr.), and ketocoumarins, as described for example inU.S. Pat. No. 4,147,552 (Specht et al.) and U.S. Pat. No. 5,455,143(Ali). Particularly useful photosensitizers for long UV and visiblelight sensitivity include but are not limited to,2-[bis(2-furoyl)methylene]-1-methyl-naphtho[1,2-d]thiazoline,2-benzoylmethylene-1-methyl-β-napthothiazoline,3,3′-carbonylbis(5,7-diethoxycoumarin),3-(7-methoxy-3-coumarinoyl)-1-methylpyridinium fluorosulfate,3-(7-methoxy-3-coumarinoyl)-1-methylpyridinium 4-toluenesulfonic acid,and 3-(7-methoxy-3-coumarinoyl)-1-methylpyridinium tetrafluoroborate.Other useful photosensitizers are described in Columns 6 and 7 of U.S.Pat. No. 4,147,552 (noted above) which disclosure of such compounds isincorporated herein by reference.

When present as individual photosensitizer compounds, thephotosensitizer components can be present in the precursor dielectriccomposition (and resulting dry gate dielectric layer) in an amount of atleast 0.1 weight % and up to and including 10 weight %, or more likelyat least 0.5 weight % and up to and including 5 weight %, based on thetotal solids in the precursor dielectric composition (or total dryweight of the gate dielectric layer).

When the photosensitizer component is provided as part of one or morerecurring units as described above (for example, (c) recurring units),it can be present in the precursor dielectric composition (and dry gatedielectric layer) in an amount of at least 1 mol % and up to andincluding 10 mol % of the recurring units based on the total recurringunits of the photocurable or thermally curable thiosulfate-containingpolymers. The exact amount of the photosensitizer component willobviously depend upon the extinction coefficient of the particularmolecule and a skilled worker can vary the amount of the (c) recurringunits or individual photosensitizer compounds appropriately for theprecursor dielectric composition.

The precursor dielectric compositions can optionally include one or moreaddenda such as other film-forming compounds (including film-formingpolymers that do not contain thiosulfate groups), surfactants,plasticizers, filter dyes, viscosity modifiers, and any other materialsthat would be readily apparent to one skilled in the art, and suchaddenda can be present in amounts that would also be readily apparent toone skilled in the art.

The essential photocurable or thermally curable thiosulfate-containingpolymer and any optional compounds described above are generallydissolved or dispersed in one or more organic solvents to form aprecursor dielectric composition that can be applied to a suitablesubstrate (described below) in any suitable manner. Useful organicsolvents include but are not limited to, alcohols such methanol,ethanol, isopropanol, n-butanol, cyclohexanol, and Dowanol™, ketonessuch as acetone and butanone, tetrahydrofuran, N,N-dimethylformamide,dioxane, toluene, and mixtures of two or more of such organic solvents.Water can be included with one or more of these organic solvents as longas water present only in amounts that would be miscible in the solventmixture.

Electronic Devices and Preparation

A method for preparing an electronic device comprises:

independently applying a precursor dielectric composition (as describedabove) and an organic semiconductor composition to a substrate to forman applied precursor dielectric layer and an applied organicsemiconductor composition, respectively, and

subjecting the applied precursor dielectric composition to curingconditions to form a gate dielectric layer comprising a photochemicallycured or thermally cured products of a photocurable or thermally curablethiosulfate-containing polymer, which gate dielectric layer is inphysical contact with the applied organic semiconductor composition.

A method of making an OFET or similar devices that include a gatedielectric layer comprises independently applying a precursor dielectriccomposition as described above, and an organic semiconductor composition(described below) to a substrate (as described below) in any suitablemanner known in the art. These compositions can be applied in anydesired order. Once applied, they are dried using known techniques. Thedried precursor dielectric composition, when cured (that can also occurat least partially during drying), then forms a gate dielectric layerthat is in physical contact with the dried organic semiconductorcomposition.

The dried precursor dielectric layer can be photocured or thermallycured using suitable curing equipment and conditions to form acrosslinked disulfide polymer product from the photocurable or thermallycurable thiosulfate-containing polymer, forming a dielectric material(or gate dielectric layer). Representative conditions for each type ofcuring are described above.

More particularly, an electronic device can be prepared using a methodcomprising:

applying a precursor dielectric composition as described above to asuitable substrate to form an applied precursor dielectric composition,

removing any solvent(s) from the applied precursor dielectriccomposition,

simultaneously or subsequently, curing the applied precursor dielectriccomposition to form a gate dielectric layer comprising a crosslinkeddisulfide polymer product (derived from the photocurable or thermallycurable thiosulfate-containing polymer),

applying an organic semiconductor composition (described below) to thegate dielectric layer to form an organic semiconductor layer (which isdried at some point), and

forming one or more sets of electrically conductive source and drainelectrodes on the dried organic semiconductor layer.

In still other embodiments, a process for fabricating a thin-filmconducting device comprises:

providing a substrate from among the materials described below (forexample, a flexible material such as a flexible polymeric film),

providing a gate electrode material over the substrate,

forming a gate dielectric layer (comprising a crosslinked disulfidepolymer product provided according to the present invention) over thegate electrode material by applying, drying, and curing a precursordielectric composition described above (generally having a dry thicknessof less than 1 μm),

providing a thin film of an organic semiconductor material to provide athin film organic semiconductor layer adjacent the gate dielectriclayer, and

providing a source electrode and a drain electrode contiguous to thethin-film of the organic semiconductor material.

Any precursor dielectric composition described herein can be used toprepare the gate dielectric layer in the OFET's or other devices, andsuch precursor dielectric compositions can comprise one or morephotocurable or thermally curable thiosulfate-containing polymersdescribed above. An integrated circuit comprising a plurality of OFET'sis also provided by the present invention when each OFET is providedusing the features described above.

Any known thin film transistor or field effect transistor configurationis possible. For example, the source and drain electrodes can beadjacent to the gate dielectric layer with the organic semiconductorlayer over the source and drain electrodes, or the organic semiconductorlayer may be interposed between the source and drain electrodes and thegate dielectric layer. In each option, the invention can provide acrosslinked disulfide polymer product in the gate dielectric layer.

Representative organic field effect transistor (OFET) are illustrated inFIGS. 1a-1d , comprising source electrode 40, drain electrode 50, gateelectrode 60, gate dielectric layer 20 comprising a crosslinkeddisulfide polymer product, substrate 10, and semiconductor organic layer30 in the form of a film connecting source electrode 40 to drainelectrode 50, which organic semiconductor layer comprises a compound asdescribed below. When the OFET operates in an accumulation mode, thecharges injected from source electrode 40 into the organic semiconductorlayer 30 are mobile and a current flows from source 40 to drain 50,mainly in a thin channel region within about 100 Angstroms of thesemiconductor-gate dielectric layer interface. In the configuration ofFIG. 1a , the charge need only be injected laterally from sourceelectrode 40 to form the channel. In the configuration of FIG. 1b , thecharge is injected vertically for source electrode 40 into organicsemiconductor layer 30 to form the channel. In the absence of a gatefield, the channel ideally has few charge carriers and as a result thereis ideally no source-drain conduction.

The off current is defined as the current flowing between sourceelectrode 40 and drain electrode 50 when charge has not beenintentionally injected into the channel by the application of a gatevoltage. For an accumulation-mode TFT, this occurs for a gate-sourcevoltage more negative, assuming an n-channel, than a certain voltageknown as the threshold voltage. The “on” current is defined as thecurrent flowing between source electrode 40 and drain electrode 50 whencharge carriers have been accumulated intentionally in the channel byapplication of an appropriate voltage to gate electrode 60, and thechannel is conducting. For an n-channel accumulation-mode TFT, thisoccurs at gate-source voltage more positive than the threshold voltage.It is desirable for this threshold voltage to be zero or slightlypositive for n-channel operation. Switching between on and off isaccomplished by the application and removal of an electric field fromgate electrode 60 across gate dielectric layer 20 to thesemiconductor-dielectric interface, effectively charging a capacitor.

In accordance with the present invention, the precursor dielectriccomposition described above can be used to provide gate dielectriclayers (also known as gate insulator layers) in the devices describedherein, to improve electrical properties, without the need foradditional surface treatment or coating another layer on the surface towhich the precursor dielectric compositions are applied.

The devices can comprise the gate dielectric layers described herein andsuch devices can be electronic device including but not limited to,organic field effect transistors (OFET's), optical devices such asorganic light emitting diodes (OLED's), photodetectors, sensors, logiccircuits, memory elements, capacitors, and photovoltaic (PV) cells.However, just because not every type of device is described in detail,it is not contemplated that the present invention is useful only toprovide OFET's. A skilled artisan in the various arts would know how touse the precursor dielectric compositions described herein for thoseother types of devices.

In one embodiment, a suitable flexible substrate (such as a polymericfilm, flexible glass, or non-conductive foil) is provided and aprecursor dielectric composition described herein is applied to thesubstrate, dried, and cured as described above, and suitable electricalcontacts are made with the resulting gate dielectric layer. Theparticular method to be used can be determined by the structure of thedesired semiconductor component. In the production of an OFET, forexample, a gate electrode can be first deposited on a flexiblesubstrate, a precursor dielectric composition can then be applied,dried, and cured onto it to form a gate dielectric layer, and thensource and drain electrodes and a layer of a suitable semiconductormaterial can be applied on top of the gate dielectric layer.

The structure of such a transistor and hence the sequence of itsproduction can be varied in the customary manner known to a personskilled in the art. For example in another embodiment, a gate electrodecan be formed first, followed by application of a precursor dielectriccomposition and gate dielectric layer formation, then the organicsemiconductor layer can be formed, and finally the contacts for thesource electrode and drain electrode can be formed on the organicsemiconducting layer.

Still another embodiment can comprise formation of the source and drainelectrodes formed first, then the organic semiconductor layer can beformed, followed by formation of the gate dielectric layer, and a gateelectrode can be formed on the gate dielectric layer.

A skilled artisan would recognize that other useful structures can beconstructed or intermediate surface modifying layers can be interposedbetween the above-described components of the thin film transistor. Inmost embodiments, a field effect transistor comprises the gatedielectric layer, a gate electrode, a organic semiconductor layer, asource electrode, and a drain electrode, wherein the gate dielectriclayer, the gate electrode, the organic semiconductor layer, the sourceelectrode, and the drain electrode are arranged in any sequence as longas the gate electrode, and the organic semiconductor layer both contactthe gate dielectric layer, and the source electrode and the drainelectrode both contact the organic semiconductor layer.

Substrates:

A substrate (sometimes known as a “support”) can be used for supportingthe gate dielectric layer and other components of an OFET or otherdevice of this invention during manufacturing, testing, or use. Askilled artisan would appreciate that a substrate that is selected forcommercial embodiments can be different from a substrate that isselected for testing or screening various embodiments. In otherembodiments, a temporary substrate can be detachably adhered ormechanically affixed to another substrate. For example, a flexiblepolymeric substrate can be adhered to a rigid glass substrate that canbe removed at some point.

In some embodiments, the substrate does not provide any necessaryelectrical function (such as electrical conductivity) for the devicesuch as an organic field effect transistor. This type of support isconsidered a “non-participating support”.

Useful substrate materials include both organic and inorganic materialsincluding but not limited to, inorganic glasses, silicon wafer, ceramicfoils, polymeric films, filled polymeric materials, coated metallicfoils, acrylics, epoxies, polyamides, polycarbonates, polyimides,polyketones,poly(oxy-1,4-phenyleneoxy-1,4-phenylenecarbonyl-1,4-phenylene)[sometimes referred to as poly(ether ether ketone) or PEEK],polynorbornenes, polyphenyleneoxides, poly(ethylene naphthalene) (PEN),poly(ethylene terephthalate) (PET), poly(phenylene sulfide) (PPS), andfiber-reinforced plastics (FRP).

Glass substrates, silicon wafers, and flexible polymeric films areparticularly useful.

A flexible substrate (for example flexible polymeric, flexible glass, orflexible composite materials) can be used in some embodiments to allowfor roll-to-roll processing (manufacturing), which can be a continuousprocess, and providing economy of scale and manufacturing compared touse of rigid supports. A flexible substrate can be designed to bewrapped around the circumference of a cylinder of less than 50 cm indiameter, or typically less than 25 cm in diameter, without distortingor breaking, using low force. A flexible substrate also can be rolledupon itself before or after manufacturing.

In some devices of the present invention, a substrate is optional. Forexample, in a top construction as illustrated in FIG. 1b , when the gateelectrode or gate dielectric layer provides sufficient support for theintended use of the resultant TFT, a substrate is not needed. Inaddition, the substrate can be combined with a temporary support inwhich the support is detachably adhered or mechanically affixed to thesubstrate, such as when the support is desired for a temporary purpose,for example, for manufacturing, testing, transport, or storage. Thus, aflexible polymeric temporary support can be adhered to a rigid glasssubstrate, which flexible polymeric temporary support could be removedat an appropriate time.

Gate Electrode:

The gate electrode for OFET's can be composed of any useful conductivematerial. A variety of useful gate materials include but are not limitedto, metals, degenerately doped semiconductors, conducting polymers, andprintable materials such as carbon ink or a silver-epoxy. For example,the gate electrode can comprise doped silicon, or a metal such asaluminum, chromium, gold, silver, nickel, palladium, platinum, tantalum,or titanium, or mixtures thereof. Conductive polymers also can be used,including but not limited to, polyaniline, polypyrrole, andpoly(3,4-ethylenedioxythiophene)/poly(styrene sulfonate) (PEDOT:PSS). Inaddition, alloys, combinations, and multilayers of these materials canbe used in the gate electrode.

In some embodiments, the same material can provide the gate electrodefunction and also provide a supporting (substrate) function. Forexample, doped silicon can function as the gate electrode and thesubstrate for an OFET.

Gate Dielectric Layer:

The gate dielectric layer (or dielectric layer) is provided on a gateelectrode to electrically insulate the gate electrode from the rest ofthe electronic device (such as an OFET device). The gate dielectriclayer is generally provided as a separate layer from a precursordielectric composition as described above. In most embodiments, the gatedielectric layer consists essentially of one of more of the crosslinkeddisulfide polymer products described above with only non-essentialmaterials as additional components. In yet other embodiments, the gatedielectric layer contains only of one or more of the crosslinkeddisulfide polymer products and an optional photosensitizer component.

The gate dielectric layers provided according to this invention exhibita suitable dielectric constant (k) that does not vary significantly withfrequency. The gate dielectric layer can have a resistivity of at least10¹⁴ ohm-cm in OFET devices.

In some embodiments, the gate dielectric layers described herein canpossess one or more of the following characteristics: they are formedfrom precursor dielectric compositions that can be applied out oforganic solutions and are crosslinkable, have high thermal stability(for example, they are stable up to a temperature of at least 250° C.),and are compatibility with flexible substrates.

For OFET's for example, the gate dielectric layer generally has anaverage dry thickness of at least 3,500 Angstroms (Å) and up to andincluding 15,000 Angstroms (Å), or typically up to and including 10,000Å, or at least 5,000 Å. The dry thickness can be determined using knownmethods such as ellipsometry and profilometry and the “average” can bedetermined from at least five separate measurements in differentlocations of the gate dielectric layer. For embedded capacitors andprinted circuit board applications, the dry gate dielectric layerthickness can include those described above for OFET's, but can also beat least 10 μm or at least 20 μm and up to and including 50 μm.

Source and Drain Electrodes:

The source electrode and drain electrode are separated from a gateelectrode by the gate dielectric layer while the organic semiconductorlayer can be over or under the source electrode and drain electrode. Thesource and drain electrodes can be composed of any useful conductivematerial including but not limited to, those materials described abovefor the gate electrode, for example, aluminum, barium, calcium,chromium, gold, silver, nickel, palladium, platinum, titanium,polyaniline, PEDOT:PSS, graphene, reduced graphene oxide (r-GO),composites of graphene, composites of reduced graphene oxide, otherconducting polymers, composites thereof, alloys thereof, combinationsthereof, and multilayers thereof.

The thin film electrodes (for example, gate electrode, source electrode,and drain electrode) can be provided by any useful means such asphysical vapor deposition (for example, thermal evaporation,sputtering), microcontact printing, flexographic printing,photolithography, or ink jet printing. The patterning of theseelectrodes can be accomplished by known methods such as shadow masking,additive photolithography, subtractive photolithography, printing,microcontact printing, and pattern coating.

The organic semiconductor layer can be provided over or under the sourceand drain electrodes, as described above in reference to the thin filmtransistor article.

Useful materials that can be formed into n-type or p-type organicsemiconductor layers are numerous and described in various publications.For example, useful semiconductor materials can be prepared usingpoly(3-hexylthiophene) (P3HT) and its derivatives, the tetracarboxylicdiimide naphthalene-based compounds described in U.S. Pat. No. 7,422,777(Shukla et al.), the N,N′-diaryl-substituted 1,4,5,8-naphthalenetetracarboxylic acid diimides having electron withdrawing groups asdescribed in U.S. Pat. No. 7,629,605 (Shukla et al.),N,N′-1,4,5,8-naphthalene tetracarboxylic acid diimides havingfluoroalkyl-substituted cycloalkyl groups as described in U.S. Pat. No.7,649,199 (Shukla et al.), heteropyrenes in p-type semiconductors asdescribed in U.S. Pat. No. 7,781,076 (Shukla et al.),cyclohexyl-substituted naphthalene tetracarboxylic acid diimides asdescribed in U.S. Pat. No. 7,804,087 (Shukla et al.),heterocyclyl-substituted naphthalene tetracarboxylic acid diimides asdescribed in U.S. Pat. No. 7,858,970 (Shukla et al.), andN,N′-arylalkyl-substituted naphthalene-based tetracarboxylic aciddiimides as described in U.S. Pat. No. 7,981,719 (Shukla et al.). Thedisclosures of all of the publications noted in this paragraph areincorporated herein by reference with respect to the noted semiconductormaterials.

The gate dielectric layers containing crosslinked disulfide polymerproducts described herein can be readily processed and are thermally andchemically stable to hot or cold organic solvents. The precursordielectric compositions described herein can be deposited by spincoating, ink jetting, or blade coating, dried, and cured as describedabove to form gate dielectric layers. The entire process of making thethin film transistors or integrated circuits can be carried out below amaximum support temperature of generally 450° C. or less, or typicallyat 250° C. or less, or even at 150° C. or less. The temperatureselection generally depends on the substrate and processing parameterschosen for the given device, once a skilled artisan has the knowledgecontained herein. These temperatures are well below traditionalintegrated circuit and semiconductor processing temperatures, whichenables the use of any of a variety of relatively inexpensive substratesmaterials, such as flexible polymeric materials. Thus, the presentinvention enables the production of relatively inexpensive integratedcircuits containing organic thin film transistors (OFET's) withsignificantly improved performance.

In one embodiment, an OFET structure illustrated in FIG. 1a is preparedby spin coating an organic semiconductor layer onto a gate dielectriclayer prepared according to this invention, which has pre-patternedsource and drain electrodes. In another embodiment, an OFET structureillustrated in FIG. 1c is prepared by spin coating an organicsemiconductor layer onto the substrate with pre-patterned source anddrain electrodes. Then, a precursor dielectric composition preparedaccording to this invention is spin coated onto the organicsemiconductor layer followed by the deposition of the gate electrode byvacuum deposition or liquid deposition of a conductive metal or metaldispersion, respectively.

Electronic devices in which OFET's and other devices are useful include,for example, more complex circuits such as shift registers, integratedcircuits, logic circuits, smart cards, memory devices, radio-frequencyidentification tags, backplanes for active matrix displays,active-matrix displays (for example liquid crystal or OLED), solarcells, ring oscillators, and complementary circuits, such as invertercircuits. In an active matrix display, a thin film transistor of thepresent invention can be used as part of voltage hold circuitry of apixel of the display. In devices containing OFET's, the OFET's areoperatively connected by means known in the art.

The electronic devices described above can comprise one or more of thedescribed thin film transistors. For example, electronic devices can beintegrated circuits, active-matrix displays, and solar cells comprisinga multiplicity of thin-film transistors. In some embodiments, themultiplicity of the thin-film transistors is on a non-participatingsupport that is optionally flexible.

The present invention provides at least the following embodiments andcombinations thereof, but other combinations of features are consideredto be within the present invention as a skilled artisan would appreciatefrom the teaching of this disclosure:

1. A precursor dielectric composition comprising:

(1) a photocurable or thermally curable thiosulfate-containing polymerthat has a T_(g) of at least 50° C. and comprises: an organic polymerbackbone comprising (a) recurring units comprising pendant thiosulfategroups; and organic charge balancing cations,

(2) optionally, an electron-accepting photosensitizer component, and

(3) one or more organic solvents in which the photocurable or thermallycurable thiosulfate-containing polymer is dissolved or dispersed.

2. The precursor dielectric composition of embodiment 1, wherein theorganic charge balancing cations form binary salts with the pendantthiosulfate groups in the (a) recurring units that are represented bythe following Structure (I):

wherein R represents the organic polymer backbone, G is a single bond ora divalent linking group, M represents an organic charge balancingcation, and “a” represents at least 0.5 mol % and up to and including100 mol % of (a) recurring units, based on the total recurring units inthe photocurable or thermally curable thiosulfate-containing polymer.

3. The precursor dielectric composition of embodiment 1 or 2, whereinthe organic charge balancing cations are part of the backbone of thephotocurable or thermally curable thiosulfate-containing polymer and notpart of pendant groups attached to the backbone.

4. The precursor dielectric composition of any of embodiments 1 to 3,wherein the organic charge balancing cations form zwitterionic groupswith the pendant thiosulfate groups in the (a) recurring units that arerepresented by the following Structure (II):

wherein R represents the organic polymer backbone, G is a single bond ordivalent linking group, Q⁺ is an organic charge balancing cation, and“a” represents at least 0.5 mol % and up to and including 100 mol % of(a) recurring units, based on the total recurring units in thephotocurable or thermally curable thiosulfate-containing polymer.

5. The precursor dielectric composition of embodiment 4, wherein Q⁺ is aquaternary ammonium cation, pyridinium cation, morpholinium cation, orthiazolium cation.

6. The precursor dielectric composition of any of embodiments 1 to 5,wherein the photocurable or thermally curable thiosulfate-containingpolymer further comprises (b) recurring units that comprise the organiccharge balancing cations, which photocurable or thermally curablethiosulfate-containing polymer is represented by the following Structure(III):

wherein R represents the organic polymer backbone, G is a single bond ora divalent linking group, M⁺ represents an organic charge balancingcation, “a” represent at least 0.5 mol % and up to and including 50 mol% of (a) recurring units, and “b” represents mol % of (b) recurringunits and is at least equal to the “a” mol %, based on the totalrecurring units in the photocurable or thermally curablethiosulfate-containing polymer.

7. The precursor dielectric composition of any of embodiments 1 to 6,wherein the photocurable or thermally curable thiosulfate-containingpolymer further comprises:

(c) recurring units that are represented by the following Structure(IV);

(d) recurring units that are represented by the following Structure (V);or

both (c) recurring units and (d) recurring units:

wherein R′ represents the organic polymer backbone, G′ is a single bondor a divalent linking group, R₂ is a electron-accepting photosensitizercomponent, and “c” represents at least 1 mol % and up to and including10 mol % of (c) recurring units, based on the total recurring units inthe photocurable or thermally-curable thio sulfate-containing polymer;

wherein R″ represents the organic polymer backbone, G″ is a carbonyloxygroup, R₃ comprises a monovalent linear, branched, or carbocyclicnon-aromatic hydrocarbon group having 1 to 18 carbon atoms, or itcomprises a phenyl group that has one or more linear, branched, orcarbocyclic non-aromatic hydrocarbon substituents, at least one of whichlinear, branched, or carbocyclic non-aromatic hydrocarbon substituentshas at least 6 carbon atoms and up to and including 18 carbon atoms, and“d” represents at least 1 mol % and up to and including 40 mol % of (d)recurring units, based on the total recurring units in the photocurableor thermally-curable thiosulfate-containing polymer.

8. The dielectric composition of any embodiments 1 to 7 that furthercomprises the electron-accepting photosensitizer component.

The following Examples are provided to illustrate the practice of thisinvention and are not meant to be limiting in any manner, and a numberof materials were prepared as described below.

Synthesis 1: Preparation of Poly(vinyl benzyl thiosulfate sodiumsalt-co-methyl methacrylate)

A representative photocurable or thermally curablethiosulfate-containing polymer useful in the practice of the presentinvention was prepared as follows:

Vinyl benzyl chloride (10 g, 0.066 mol), methyl methacrylate (26.23 g,0.262 mol), and AIBN (1.08 g, 7 mmol) were dissolved 180 ml of toluene.The resulting reaction solution was purged with dry nitrogen and thenheated at 65° C. overnight. After cooling the reaction solution to roomtemperature, it was dropwise added to 2000 ml of methanol. The resultingwhite powdery copolymer was collected by filtration and dried undervacuum at 60° C. overnight. 1H NMR analysis indicated that the resultingcopolymer contained 30 mol % of recurring units derived from vinylbenzyl chloride.

A sample of this copolymer (18 g) was dissolved in 110 ml ofN,N-dimethyl formamide (DMF). To this solution was added sodiumthiosulfate (9 g) and 20 ml of water. Some copolymer precipitated out.The cloudy reaction mixture was heated at 70° C. for 24 hours. Aftercooling to room temperature, the hazy reaction mixture was transferredto a dialysis membrane and dialyzed against water. A small amount of theresulting copolymer solution was freeze dried for elemental analysis andthe rest was stored for use as a solution. Elemental analysis indicatedthat all the benzyl chloride groups in the copolymer were converted tosodium thiosulfate salt to provide a photocurable or thermally-curablethiosulfate-containing polymer useful in the present invention.

Synthesis 2: Preparation ofN-butyl-N′-[2-(ethoxy-2-acrylate)ethyl]-1,4,5,8-naphthalenetetracarboxylicdiimide

A representative ethylenically unsaturated polymerizable monomer usefulto provide photocurable or thermally-curable thiosulfate-containingpolymers of the present invention was prepared in the following manner.

Step 1: Synthesis of the monopotassium salt (half anhydride),1-potassium carboxylate-8-carboxylic acid naphthalene-4,5-dicarboxylicanhydride:

A 12-liter, four-neck round bottom flask fitted with a mechanicalstirrer and a condenser was charged with potassium hydroxide (454 g,7.60 mol) and water (6 liters), followed by the addition of1,4,5,8-naphthalenetetra-carboxylic dianhydride (462 g, 1.72 mol). Thereaction mixture was stirred for 1 hour and a clear solution resulted.Phosphoric acid, 85% (613 g, 5.2 mol) in water (900 ml), was added over45 minutes, the reaction solution was stirred overnight, and theresulting solid product was collected by filtration (yield close to100%.) The spectral data were consistent with its assigned structure.

Step 2: Synthesis of monoimide,naphthalenetetracarboxylic-1,8-N-butylimide-4,5-anhydride:

A 12-liter, four-neck round bottom flask fitted with a mechanicalstirrer and a condenser was charged with the monopotassium salt obtainedin Step 1 (169.2 g, 0.52 mol) and water (5 liters) to give a milkybrown-colored suspension. Butyl amine (240 g, 3.12 mol) was added all atonce and a clear amber-colored solution was formed. The reactionsolution was heated to 90-95° C. for 1 hour. Concentrated hydrochloricacid (690 ml) dissolved in 700 ml of water was added dropwise to the hotreaction solution and heating was continued for 2 hours. During theaddition, the temperature did not exceed 95° C. Heat was removed and thereaction was allowed to stir overnight at room temperature. Theresulting precipitate was collected on a glass frit to give 150 g of thedesired product at 90% yield. Spectral data were consistent with theassigned compound structure.

Step 3: Synthesis of diimide,N-butyl-N′-[2-(2-hydroxyethoxy)-ethyl]-1,4,5,8-naphthalenetetraccarboxylicdiimide:

A 12-liter, four-neck round bottom flask fitted with a mechanicalstirrer and a condenser was charged with naphthalene butylimidemonoanhydride (434 g, 1.4 mol) from Step 2, 2-(2-aminoethoxyethanol (230g, 2.2 mol), and N-methyl pyrrolidone (1.2 liters). The reactionsolution was heated to 140-150° C. for 3 hours. The reaction solutionwas then allowed to cool for 30 minutes and the reaction flask wasfilled with methanol and a pink-colored solid precipitated. The reactionsolution was stirred overnight and the resulting solid was collected ona glass frit to give 522 g of crude product (90% yield). Purificationwas carried out using dichloromethane on a silica gel column, providing313 g of product (54% yield). The spectral data were consistent with theassigned compound structure.

Step 4: Coupling of naphthalene bisimide alcohol with acryloyl chloride,N-butyl-N′-[2-(ethoxy-2-acrylate)ethyl]-1,4,5,8-naphthalene-tetracarboxylic diimide with acryloylchloride:

A 5-liter, four-neck round bottom flask fitted with a mechanicalstirred, condenser and a nitrogen inlet was charged with the hydroxylether naphthalene butyl bisimide of Step 3 (246 g, 0.6 mol) andtriethylamine (73 g, 0.72 mol, 100 ml) in dichloromethane (2 liters).Acryloyl chloride (63 g, 0.7 mol, 57 ml) in dichloromethane (DCM, 150ml) was added dropwise, solubilizing the reactants and the reactionsolution was stirred at room temperature overnight. The reactionsolution was washed with 5% hydrochloride acid (200 ml), forming anemulsion. Methanol was added to break up the emulsion. The organicproducts were washed with water and dried over magnesium sulfate. Theresulting product was purified on silica column using ligroin/DCMmixture at 1/1 then increasing to 100% DCM to elute the product. Thespectral data were consistent with the assigned compound structure.

Synthesis 3: Preparation of 1,8-Naphthalimidohexyl Acrylate

A representative ethylenically unsaturated polymerizable monomer usefulto provide thiosulfate polymers of the present invention was prepared asfollows:

Step 1—Synthesis of 1,8-Naphthalimidohexanol (diimide):

A 200 ml round bottom flask fitted with condenser, nitrogen inlet, andstirring magnet was charged with 1,8-naphthalic anhydride (10 g, 50.5mmol), 6-amino-1-hexanol (6 g, 51.0 mmol), and 150 ml ofN-methyl-2-pyrrolidone. The reaction mixture was warmed to 140° C. for20 hours. The reaction mixture was then cooled and poured into excessice water. A resulting brown precipitate was filtered and recrystalyzedfrom heptane to give 5 grams of a tan colored solid (30% yield). Thespectral data were consistent with assigned compound structure.

Step 2—Synthesis of 1,8-Naphthalimidohexyl acrylate:

A 200 ml 3-neck round flask with a nitrogen inlet, and stirring magnetwas charged with the 1,8-naphthalimidohexanol (2.1 g, 7.1 mmol) and 60ml of anhydrous dichloromethane.

Once dissolved, triethylamine (0.9 g, 9.2 mmol) was added. To thisstirring mixture was slowly added acryloyl chloride (0.8 g, 9.2 mmol).The reaction mixture was allowed to stir at room temperature for 24hours. The reaction mixture was washed once with 10% HCl, then withwater, and dried over magnesium sulfate, and the solvent was removed invacuo to provide a yellow semisolid. The resulting crude product waspurified by running it through column of silica with dichloromethane toelute the final product. The spectral data were consistent with theassigned compound structure.

Synthesis 4: Preparation of Poly(2-hydroxy-2-thiosulfate sodium saltpropyl methacrylate-co-methyl methacrylate)

The procedure of Synthesis 1 was followed using glycidyl methacrylate(18.2 g, 0.128 mol), methyl methacrylate (30.0 g, 0.300 mol),2,2′-azobis(2-methylbutyronitrile) (0.82 g, 0.004 mol), and 192 ml oftoluene. The reaction temperature was 70° C. 1H NMR analysis indicatedthat the resulting precursor polymer contained 35 mol % of recurringunits derived from glycidyl methacrylate. Analysis by size exclusionchromatography (SEC) indicated a weight average molar mass of 45,800(polystyrene standards)

The desired photocurable or thermally-curable thiosulfate-containingpolymer was prepared as described for Synthesis 1 using 30.0 g of theprecursor polymer, 140 ml of DMF, 16.8 g of sodium thiosulfate, and 28ml of water. The temperature of the reaction solution was 70° C. for 24hours. The glass transition temperature of the resulting photocurable orthermally-curable thiosulfate-containing polymer was determined to be107.5° C. by Differential Scanning calorimetry (DSC).

Synthesis 5: Preparation of Poly(vinyl benzyl thiosulfate sodiumsalt-co-methyl methacrylate-co-octyl methacrylate)

Vinyl benzyl chloride (5.00 g, 0.033 mol), methyl methacrylate (7.30 g,0.073 mol), octyl methacrylate (0.793 g, 0.004 mole), and2,2′-azobis(2-methylbutyronitrile) (0.20 g, 0.001 mol), were dissolved52.0 ml of toluene. The resulting reaction solution was purged with drynitrogen and then heated at 70° C. overnight. After cooling the reactionsolution to room temperature, it was dropwise added to 2000 ml ofmethanol. The resulting white powdery precursor polymer was collected byfiltration and dried under vacuum at 60° C. overnight. 1H NMR analysisindicated that the resulting copolymer contained 30 mol % of recurringunits derived from vinyl benzyl chloride. Analysis by size exclusionchromatography (SEC) indicated a weight average molar mass of 35,200(polystyrene standards).

The desired photocurable or thermally-curable thiosulfate-containingpolymer was prepared as described for Synthesis 1 using 5.0 g of theprecursor polymer, 23 ml of DMF, 2.8 g of sodium thiosulfate, and 5 mlof water. The temperature of the reaction solution was 70° C. for 24hours. The glass transition temperature of the resulting photocurable orthermally-curable thiosulfate-containing polymer was determined to be100.5° C. by Differential Scanning calorimetry (DSC).

Synthesis 6: Polyurethane with Thiosulfate Groups

Polycarbonate (5.40 g, 0.003 mol), 2,3 dibromo-1,4-butanediol (1.90 g,0.008 mol), and a catalytic amount of dibutyltin dilaurate weredissolved 13 ml of tetrahydrofuran and warmed to 65° C. To this wasadded (under nitrogen) isophorone diisocyanate (2.5 g, 0.011 mol)dropwise. The reaction mixture was maintained at 70° C. for 20 hours,cooled and precipitated into heptanes. The resulting polymer wascollected by filtration and dried under vacuum at 70° C. overnight. 1HNMR analysis indicated that the resulting precursor polymer contained 24mol % of recurring units derived from dibromobutanediol. Analysis bysize exclusion chromatography (SEC) indicated a weight average molarmass of 20,600 (polystyrene standards).

The desired photocurable or thermally-curable thiosulfate-containingpolymer was prepared as described for Synthesis 1 using 3.0 g of theprecursor polymer, 40 ml of DMF, 1.0 g of sodium thiosulfate, and 8 mlof water. The temperature of the reaction solution was maintained at 70°C. for 24 hours. The resulting thiosulfate-containing polyurethane isshown as follows with the three different types of recurring units.

Inventive Example 1: Preparation of Poly(vinyl benzyl thiosulfate sodiumsalt-co-methylmethacrylate-co-N-butyl-N′-[2-(ethoxy-2-acrylate)ethyl]-1,4,5,8-naphthalenetetracarboxylicdiimide)

The procedure of Synthesis 1 was followed using vinyl benzyl chloride(4.2 g, 0.027 mol), methyl methacrylate (8.5 g, 0.085 mol),1,8-naphthalimidohexanol (1.1 g, 0.002 mol),2,2′-azobis(2-methylbutyronitrile) (0.33 g, 0.002 mol), and 47 ml oftoluene. The reaction temperature was 70° C. 1H NMR analysis indicatedthat the resulting precursor polymer contained 30 mol % of recurringunits derived from vinyl benzyl chloride. Analysis by size exclusionchromatography (SEC) indicated a weight average molar mass of 17,800(polystyrene standards).

The desired photocurable or thermally curable thiosulfate-containingpolymer was prepared as described in Synthesis 1 using 1.35 g of theprecursor polymer, 50 ml of DMF, 1.5 g of sodium thiosulfate, and 10 mlof water. The temperature of the reaction solution was 90° C. for 8hours. The glass transition temperature of the photocurable orthermally-curable thiosulfate-containing polymer was determined to be99.8° C. by Differential Scanning calorimetry (DSC).

Inventive Example 2: Preparation of Poly(vinyl benzyl thiosulfate sodiumsalt-co-methyl methacrylate-co-acrylicacid-co-N-butyl-N′-[2-(ethoxy-2-acrylate)ethyl]-1,4,5,8-naphthalene-tetracarboxylicdiimide)

The procedure of Synthesis 1 was followed using vinyl benzyl chloride(8.2 g, 0.053 mol), methyl methacrylate (8.5 g, 0.085 mol), acrylic acid(8.5 g, 0.119 mol), 1,8-naphthalimidohexanol (2.3 g, 0.005 mol),2,2′-azobis(2-methylbutyronitrile) (0.76 g, 0.004 mol), and 90 ml ofdioxane. The reaction temperature was 70° C. ¹H NMR analysis indicatedthat the resulting precursor polymer contained 30 mol % of recurringunits derived from vinyl benzyl chloride. Analysis by size exclusionchromatography (SEC) indicated a weight average molar mass of 41,600(polystyrene standards).

The desired photocurable or thermally-curable thiosulfate-containingpolymer was prepared as described in Synthesis 1 using 26.1 g of theprecursor polymer, 285 ml of DMF, 8.5 g sodium thiosulfate, and 57 ml ofwater. The temperature of the reaction solution was held at 90° C. for 8hours. The glass transition temperature of the resulting photocurable orthermally-curable thiosulfate-containing polymer was determined to be195° C. by Differential Scanning calorimetry (DSC).

Inventive Example 3: Preparation of Poly(vinyl benzyl thiosulfate sodiumsalt-co-acrylic acid-co-N-butyl-N′-[2-(ethoxy-2-acrylate)ethyl]-1,4,5,8-naphthalenetetracarboxylic diimide)

The procedure of Synthesis 1 was followed using vinyl benzyl chloride(7.3 g, 0.048 mol), acrylic acid (15.0 g, 0.21 mol),1,8-naphthalimidohexanol (1.9 g, 0.005 mol),2,2′-azobis(2-methylbutyronitrile) (0.76 g, 0.004 mol), and 73 ml ofdioxane. The reaction temperature was 70° C. 1H NMR analysis indicatedthat the resulting precursor polymer contained 31 mol % of recurringunits derived from vinyl benzyl chloride. Analysis by size exclusionchromatography (SEC) indicated a weight average molar mass of 21,400(polystyrene standards).

The desired photocurable or thermally-curable thiosulfate-containingpolymer was prepared as described in Synthesis 1 using 20.0 g of theprecursor polymer, 250 ml of DMF, 6.5 g sodium thiosulfate, and 50 ml ofwater. The reaction temperature was 90° C. for 8 hours to provide thedesired photocurable or thermally-curable thiosulfate-containing polymerthat had a glass transition temperature of 200° C. as determined by DSC.

Inventive Example 4: Preparation of Poly(vinyl benzyl thiosulfate sodiumsalt-co-methyl methacrylate-co-1,8-naphthalimidohexyl acrylate)

The procedure of Synthesis 3 was followed using vinyl benzyl chloride(3.5 g, 0.023 mol), methyl methacrylate (7.7 g, 0.077 mol),1,8-naphthalimidohexanol (0.5 g, 0.001 mol),2,2′-azobis(2-methylbutyronitrile) (0.29 g, 0.002 mol), and 40 ml oftoluene. 1H NMR analysis indicated that the desired precursor polymercontained 34 mol % of recurring units derived from vinyl benzylchloride, and analysis by size exclusion chromatography (SEC) indicateda weight average molar mass of 25,800 (polystyrene standards).

The desired photocurable or thermally-curable thiosulfate-containingpolymer was prepared as described in Synthesis 1 using 8.0 g of theprecursor polymer, 40 ml of DMF, 3.9 g of sodium thiosulfate, and 8 mlof water. The reaction temperature was held at 90° C. for 8 hours toprovide the desired photocurable or thermally-curablethiosulfate-containing polymer that had a glass transition temperatureof 111° C. as measured by DSC.

Inventive Example 5: Preparation of Poly(vinyl benzyl thiosulfate sodiumsalt-co-methyl methacrylate-co-acrylic acid-co-1,8-naphthalimidohexylacrylate)

The procedure of Synthesis 1 was followed using vinyl benzyl chloride(3.0 g, 0.02 mol), methyl methacrylate (3.6 g, 0.036 mol), acrylic acid(3.0 g, 0.04 mol), 1,8-naphthalimidohexanol (0.4 g, 0.001 mol),2,2′-azobis(2-methylbutyronitrile) (0.28 g, 0.002 mol), and 30 ml ofdioxane. 1H NMR analysis indicated that the resulting precursor polymercontained 33 mol % of vinyl benzyl chloride, and analysis by SECindicated a weight average molar mass of 45,200 (polystyrene standards).

The desired photocurable or thermally-curable thiosulfate-containingpolymer was prepared as described in Synthesis 3 using 4.2 g of theprecursor polymer, 22.5 ml of DMF, 2.1 g of sodium thiosulfate, and 4.5ml of water. The reaction temperature was held at 90° C. to provide thedesired photocurable or thermally-curable thiosulfate-containing polymerthat had a glass transition temperature of 119° C. as determined by DSC.

Preparation of Gate Dielectric Layer and Dielectric Constant MeasurementInvention Example 6

A 7 weight % water solution of a photocurable or thermally-curablethiosulfate-containing polymer, poly(vinyl benzyl thiosulfate sodiumsalt-co-methyl methacrylate) (structure shown above; synthesis describedin Invention Example 1) was filtered through a Whatman 0.45 μm glassmicrofiber filter into a clean glass vial or container. A filteredprecursor dielectric composition containing this polymer was spun castonto a heavily doped silicon wafer substrate for 10 seconds at 1100 rpmand the coating speed was increased over 30 seconds to 3,000 rpm andspun at this speed for 40 seconds. To provide thermal curing, the coateddielectric composition film was then placed on a hot plate and graduallyheated from 50° C. to 140° C. over a period of 15 minutes. Finally, thetemperature was increased to 150° C. and was held there for 30 minutes.The resulting dry gate dielectric layer containing crosslinked polymerwas gradually cooled to room temperature over a period of 30 minutes.Its dry thickness was in the range of from 350 nm to 400 nm.

The capacitance of the resulting gate dielectric layer was measured withan impedance analyzer (Hewlett Packard 4192A) at a frequency of 10 kHz.Each substrate was a heavily doped Si wafer. Silver layers with an areaof approximately 5×10⁻⁷ m² and patterned as upper electrodes on thesurface of each composite structure were deposited in vacuum through ashadow mask. The dielectric constant of the composite structure wasestimated from the capacitance of the gate dielectric layer, the area ofthe silver upper electrode, and the gate dielectric layer thickness.

The dielectric constant of the thermally crosslinked poly(vinyl benzylthiosulfate sodium salt-co-methyl methacrylate)-containing gatedielectric layer is shown below in TABLE I.

Invention Example 7

To a water solution of a photocurable or thermally-curablethiosulfate-containing polymer, poly(vinyl benzyl thiosulfate sodiumsalt-co-methyl methacrylate), a stoichiometric amount oftetrabutylammonium chloride was added and solution stirred for 10-20minutes. An aqueous solution of the resulting polymer was transferredinto a separatory funnel and extracted with methylene chloride. Combinedmethylene chloride extracts were dried over anhydrous MgSO4, filtered,and evaporated to obtain a white powder of poly(vinyl benzyl thiosulfatetetrabutylammonium salt-co-methyl methacrylate).

A 6 weight % solution of poly(vinyl benzyl thiosulfatetetrabutylammonium salt-co-methyl methacrylate) in methylene chlorideand 1-methoxy-2-isopropanol (3:1 v/v) was spin coated as a precursordielectric composition onto a doped silicon wafer as a substrate. Thecoated dielectric composition was then placed onto a hot plate andgradually heated from 50° C. to 140° C. over a period of 15 minutes.Finally, the temperature was increased to 150° C. and was held for 30minutes. The thermally cured gate dielectric layer was gradually cooledto room temperature over a period of 30 minutes. The thickness of thegate dielectric layer was in the range of from 350 nm to 400 nm.

The capacitance of the gate dielectric layer was measured with animpedance analyzer (Hewlett Packard 4192A) at a frequency of 10 kHz. Thesubstrate was a heavily doped Si wafer. Silver layers with an area ofapproximately 5×10⁻⁷ m² as upper electrodes were patterned on thesurface of each composite were deposited in vacuum through a shadowmask. The dielectric constant of the composite film was estimated fromthe capacitance of the gate dielectric layer, area of the silverelectrode, and gate dielectric layer thickness.

The dielectric constant of the gate dielectric layer is shown below inTABLE I.

TABLE I Dielectric constant Invention Polymer x y (k) @ 10 kHz

0.67 0.86 0.92 0.33 0.14 0.08 4.1 (+/− 0.1) 3.6 (+/− 0.1) 3.1 (+/− 0.1)

0.67 0.33 4.1 (+/− 0.1)

The following examples demonstrate that organic thin film transistordevices comprising photocrosslinked polymers derived from photocurableor thermally-curable thiosulfate-containing polymers in gate dielectriclayers according to the present invention exhibited high mobilities andon/off ratios.

Organic Thin Film Transistor Device Preparation:

In order to test the electrical characteristics of the various gatedielectric layers according to the present invention, organicfield-effect transistors were made using the top-contact geometry asillustrated in FIGS. 1c and 1d . The substrate used was a heavily dopedsilicon wafer that also served as the gate of each transistor. The gatedielectric layers were obtained from photocurable or thermally-curablethiosulfate-containing polymers in precursor dielectric compositionsspun coated onto the substrate to have a dry thickness of 300-400 nm.

Device Measurement and Analysis

Electrical characterization of the fabricated electronic devices wasperformed using a Hewlett Packard HP 4145B® parameter analyzer. Theprobe measurement station was held in a positive argon environment forall measurements with the exception of those purposely used to test thestability of the devices in air. The measurements were performed undersulfur lighting unless sensitivity to white light was beinginvestigated. The electronic devices were exposed to air prior totesting.

For each experiment performed, between 4 and 12 individual electronicdevices were tested using each prepared organic semiconductor layer, andthe results were averaged. For each electronic device, the drain current(I_(d)) was measured as a function of source-drain voltage (V_(d)) forvarious values of gate voltage (V_(g)). For most electronic devices,V_(d) was swept from 0 V to 80 V for each of the gate voltages measured,typically 0 V, 20 V, 40 V, 60 V, and 80 V. In these measurements, thegate current (I_(g)) was also recorded in order to detect any leakagecurrent through the device. Furthermore, for each device the draincurrent was measured as a function of gate voltage for various values ofsource-drain voltage. For most devices, V_(g) was swept from 0 V to 80 Vfor each of the drain voltages measured, typically 40 V, 60 V, and 80 V.

Parameters extracted from the data include field-effect mobility (μ),threshold voltage (V_(t)), sub-threshold slope (S), and the ratio ofI_(on)/I_(off) for the measured drain current. The field-effect mobilitywas extracted in the saturation region, where V_(d)>V_(g)−V_(t). In thisregion, the drain current is given by the equation [see Sze,Semiconductor Devices—Physics and Technology, John Wiley & Sons (1981)]:

$I_{d} = {\frac{{WC}_{0}}{2\; L}{\mu\left( {V_{g} - V_{t}} \right)}^{2}}$$\sqrt{I_{d}} = {\sqrt{\frac{\mu\; C_{0}W}{2\; L}}\left( {V_{g} - V_{t}} \right)}$${slope} = \sqrt{\frac{\mu\; C_{0}W}{2\; L}}$$\mu = {({slope})^{2}\frac{2\; L}{C_{0}W}}$wherein W and L are the channel width and length, respectively, andC_(o) is the capacitance of the oxide layer, which is a function ofoxide thickness and dielectric constant of the material. Given thisequation, the saturation field-effect mobility was extracted from astraight-line fit to the linear portion of the √I_(d) versus V_(g) curve(as described above). The threshold voltage, V_(t), is the x-interceptof this straight-line fit. Mobilities can also be extracted from thelinear region, where V_(d)≦V_(g)−V_(t). The drain current is given bythe following equation (see Sze, noted above):

$I_{d} = {\frac{W}{L}\mu\;{C_{o}\left\lbrack {{V_{d}\left( {V_{g} - V_{t}} \right)} - \frac{V_{d}^{2}}{2}} \right\rbrack}}$

For these experiments, mobilities in the linear regime were notextracted, since this parameter is very much affected by any injectionproblems at the contacts. In general, non-linearity in the curves ofI_(d) versus V_(d) at low V_(d) indicates that the performance of thedevice is limited by injection of charge by the contacts. In order toobtain results that are largely independent of contact imperfections ofa given device, the saturation mobility rather than the linear mobilitywas extracted as the characteristic parameter of device performance.

The log of the drain current as a function of gate voltage was plotted.Parameters extracted from the log I_(d) plot include the I_(on)/I_(off)ratio and the sub-threshold slope (S). The I_(on)/I_(off) ratio issimply the ratio of the maximum to minimum drain current, and S is theinverse of the slope of the I_(d) curve in the region over which thedrain current is increasing (that is, the device is turning on).

Organic Semiconductors:

n-Type organic semiconductors A-1 and A-2 that were used to fabricateOFET devices in comparative and inventive examples have been previouslydescribed in U.S. Pat. No. 7,422,777 (Shukla et al.) and U.S. Pat. No.7,804,087 (Shukla et al.). Compounds A-1 and A-2 (shown below) wereprepared and purified following procedures described in these twopatents and these preparations are incorporated herein by reference,

Invention Example 8

Thiosulfate containing polymer (x=0.67; y=0.33) described in aboveInvention Example 6 of the present invention was coated onto Si wafersas and thermally cured as described in Invention Example 7. A 0.3 weight% solution of organic semiconductor, A-1 (shown above and as disclosedin U.S. Pat. No. 7,804,087 of Shukla et al. the disclosure of which isincorporated herein by reference) in a mixture of mesitylene and1,2,4-trimethylbenzene (1:3 v/v) was spin coated onto the dry gatedielectric layer at 800 rpm and dried at 70° C. for 15 minutes. Silvercontacts having a thickness of 50 nm were then deposited through ashadow mask. The channel width was held at 1000 μm while the channellengths were varied between 50 μm and 150 μm. For each thin filmtransistor, the field effect mobility, μ, was calculated from the slopeof the (I_(d))^(1/2) versus V_(G) plot. The average mobility was foundto be 0.014 cm²/V·sec in the saturation region, the average on-off ratiowas 3×10³, and the average threshold voltage was 70 V. Saturationmobilities of up to and including 0.02 cm²/V·sec were measured for thesedevices.

In a different experiment, organic semiconductor A-2 (shown above) wasdeposited by vacuum deposition in a thermal evaporator. The depositionrate was 0.1 Angstroms per second while the substrate temperature washeld at 25° C. for most experiments. The thickness of the resultingorganic semiconductor layer was a variable in some experiments but wastypically 25 nm. The average mobility in devices with A-2 semiconductorwas found to be 0.7 cm²/V·sec in the saturation region, the averageon-off ratio was 3×10⁵, and the average threshold voltage was 43 V.Saturation mobilities of up to and including 1.0 cm²/V·sec were measuredfor these devices.

The invention has been described in detail with particular reference tocertain desirable embodiments thereof, but it will be understood thatvariations and modifications can be effected within the spirit and scopeof the invention.

PARTS LIST

-   10 Substrate-   20 Gate dielectric layer-   30 Semiconductive organic layer-   40 Source electrode-   50 Drain electrode-   60 Gate electrode

The invention claimed is:
 1. A precursor dielectric composition comprising: (1) a photocurable thiosulfate-containing polymer that has a T_(g) of at least 50° C. and comprises: an organic polymer backbone comprising (a) recurring units comprising pendant thiosulfate groups; and organic charge balancing cations, (2) an electron-accepting photosensitizer component, and (3) one or more organic solvents in which the photocurable or thermally curable thiosulfate-containing polymer is dissolved or dispersed.
 2. The precursor dielectric composition of claim 1, wherein the organic charge balancing cations form binary salts with the pendant thiosulfate groups in the (a) recurring units that are represented by the following Structure (I):

wherein R represents the organic polymer backbone, G is a single bond or a divalent linking group, M represents an organic charge balancing cation, and “a” represents at least 0.5 mol % and up to and including 100 mol % of (a) recurring units, based on the total recurring units in the photocurable or thermally curable thiosulfate-containing polymer.
 3. The precursor dielectric composition of claim 1, wherein the organic charge balancing cations are part of the backbone of the photocurable or thermally curable thiosulfate-containing polymer and not part of pendant groups attached to the backbone.
 4. The precursor dielectric composition of claim 1, wherein the organic charge balancing cations form zwitterionic groups with the pendant thiosulfate groups in the (a) recurring units that are represented by the following Structure (II):

wherein R represents the organic polymer backbone, G is a single bond or divalent linking group, Q⁺ is an organic charge balancing cation, and “a” represents at least 0.5 mol % and up to and including 100 mol % of (a) recurring units, based on the total recurring units in the photocurable or thermally curable thiosulfate-containing polymer.
 5. The precursor dielectric composition of claim 4, wherein Q⁺ is a quaternary ammonium cation, pyridinium cation, morpholinium cation, or thiazolium cation.
 6. The precursor dielectric composition of claim 1, wherein the photocurable or thermally curable thiosulfate-containing polymer further comprises (b) recurring units that comprise the organic charge balancing cations, which photocurable or thermally curable thiosulfate-containing polymer is represented by the following Structure (III):

wherein R represents the organic polymer backbone, G is a single bond or a divalent linking group, M⁺ represents an organic charge balancing cation, “a” represent at least 0.5 mol % and up to and including 50 mol % of (a) recurring units, and “b” represents mol % of (b) recurring units and is at least equal to the “a” mol %, based on the total recurring units in the photocurable or thermally curable thiosulfate-containing polymer.
 7. The precursor dielectric composition of claim 1, wherein the photocurable or thermally curable thio sulfate-containing polymer further comprises: (c) recurring units that are represented by the following Structure (IV); (d) recurring units that are represented by the following Structure (V); or both (c) recurring units and (d) recurring units:

wherein R′ represents the organic polymer backbone, G′ is a single bond or a divalent linking group, R₂ is a electron-accepting photo sensitizer component, and “c” represents at least 1 mol % and up to and including 10 mol % of (c) recurring units, based on the total recurring units in the photocurable or thermally-curable thiosulfate-containing polymer;

wherein R″ represents the organic polymer backbone, G″ is a carbonyloxy group, R₃ comprises a monovalent linear, branched, or carbocyclic non-aromatic hydrocarbon group having 1 to 18 carbon atoms, or it comprises a phenyl group that has one or more linear, branched, or carbocyclic non-aromatic hydrocarbon substituents, at least one of which linear, branched, or carbocyclic non-aromatic hydrocarbon substituents has at least 6 carbon atoms and up to and including 18 carbon atoms, and “d” represents at least 1 mol % and up to and including 40 mol % of (d) recurring units, based on the total recurring units in the photocurable or thermally-curable thiosulfate-containing polymer.
 8. A precursor dielectric composition comprising: (1) a photocurable or thermally curable thiosulfate-containing polymer that has a T_(g) of at least 50° C. and comprises: an organic polymer backbone comprising (a) recurring units comprising pendant thiosulfate groups; and organic charge balancing cations, (2) optionally, an electron-accepting photosensitizes component, and (3) one or more organic solvents in which the photocurable or thermally curable thiosulfate-containing polymer is dissolved or dispersed, wherein the organic charge balancing cations form binary salts with the pendant thiosulfate groups in the (a) recurring units that are represented by the following Structure (I):

wherein R represents the organic polymer backbone, G is a single bond or a divalent linking group, M represents an organic charge balancing cation, and “a” represents at least 0.5 mol % and up to and including 100 mol % of (a) recurring units, based on the total recurring units in the photocurable or thermally curable thiosulfate-containing polymer, and the one or more organic solvents are selected from methylene chloride, methoxy-2-isopropanol, a glycol ether, toluene, dimethyl formamide, or a mixture of two or more of such organic solvents. 